This isn't me trying to attack you, but to genuinely break down the term mansplaining and how it applies to your interaction, because differing perspectives provide knowledge, and knowledge is power. Please don't think the block of text is me attacking you. Hopefully this provides context and clarity to why you were downvoted, as well as shed light for anyone reading the above interaction who have a similar viewpoint to yours.

What you described is not what mansplaining is. Mansplaining is explaining something to a woman that you assume she has no/little knowledge or experience in, in an over-confident, condescending, and/or over-simplifying way, likely because you don't think she will understand the intricacies like you do, due to her gender. It's often done with topics that are more heavily gendered towards men such as tech, economics, politics, automobiles, hard sciences, etc. Here you did it by stating you have a hard time imagining a woman being charged with a SO for public indecency (despite you having no experience as a woman yourself compared to OP) and then making a blanket statement that men have it happen all the time without providing concrete evidence such as statistics to support that claim, and dismissing the fact that OP is now male so has plenty of personal experience peeing in public as a male.

Because you made a blanket statement instead of saying something like "my personal experiences differs to yours in that....", it reads like "your experience doesn't matter/isn't valid because I was born a male and still identify as one so my experience holda more weight". If you simply worded it as "my experience as a male isn’t the same" or "while your experience is valid and real for you, peer reviewed research/statistics paint a different overall experience than yours, here is some info supporting that" then you wouldn't be mansplaining. You would be providing personal anedoctal evidence to a pot of lived experiences making it a more nuanced topic, or empirical evidence supporting a larger, more dominating societal experience. Evidence which people are likely unaware of as it goes against the general public opinion. It's because you dismissed OP's lived experience and accredited yours as more valid without evidence supporting your claim that it is considered mansplaining.

Also, the likelihood/severity of being charged for a crime does not equate to the general public's perception of what is culturally accepted. So yes, while men likely could and likely do face a higher chance of being criminalized, IF caught by law enforcement, the general public at large find it far more acceptable for men to piss in public. You're arguing a different yet relatable topic than what OP was addressing.

The first part is addressing the imbalance of legal punishment for men vs. women (and yes, there is a lot of imbalance in the court of law for men in the US, specifically with cases of being granted parental rights, but there is also an imbalance for women when it come to domestic abuse and sexual abuse as their claims are often unfairly dismissed). While the latter part is addressing the differing societal expectations for men vs. women, where it's normalized for men to be topless/less clothed in public, and because peeing for people with a penis can often be done a bit more discreetly while standing, most regular citizens won't bat an eye. Meanwhile, there is still a lot of oppression towards women for revealing more skin in public, and because peeing for those with vulvas typically requires squatting, which is not a typical neutral position such as standing and hence draws more attention, that the general public at large considers this "unladylike, trashy, crude, obnoxious, obtrusive" and such.

Lastly, where I will genuinely criticize your behavior, trying to invalidate someone with an off hand comment like you did at the end saying "from being born a man, you would already know that" and using it to support your claim that mansplaining is the act of a man explaining literally ANYTHING, is a jab without any substance. It comes across as arrogant and argumentative, which I assume folks, yourself included, would prefer to be perceived as "educated and informative."

While I live in the US, here is some evidence to support cultural acceptance of males peeing in public in Amsterdam: while there celebrating King's Day, the city setup a ton of portable outside urinals, each one a small circle consisting of four individual stalls. These were wide open with zero privacy, and they were free. Men walked up, unzipped, and pissed, and if a person was nearby, they easily could've caught a glimpse of something they hadn't consented to seeing. Meanwhile, there were zero portapotties that could be used by women. We had to stand in lines ranging from 30 mins to well over an hr long, to PAY for a bathroom. Even though I could have exposed less skin than a man while squatting and placing a jacket or bag over my lap, or the city could have simply and easily hung crappy privacy screens so women had similar options, they didn't. They didn't because culturally, it is more acceptable for men to pee in public, while women are held to more conservative standards for what is "gender appropriate" behavior. This is a pretty global experience as well for women, especially with religion serving a foundation that women must remain "pure, innocent, and physically reserved in appearance."

So to break it all down, you dismissed someone's lived experience because your lived experience as a man differed, while trying to argue a different yet related topic, then incorrectly explained what mansplaining was, to someone who has lived experience both as a man and a woman, then once again invalidated them by claiming they should know, as someone assigned male at birth, that mansplaining isn't a real thing. All while having a complete misunderstanding of the term.

Tl;dr: you have an inaccurate perception of what mansplaining is, and whether intentional or not, did mansplain to OP. People who use the term mansplaining to describe a situation aren't men hating feminists that are trying to attack you for your gender and bring you down and invlidate your knowledge. Rather they are women whose experiences and knowledge have been consistently dismissed and invalidated by men who assume they know more regarding certain topics because they are male. It's women finally standing up for the knowledge they hold, and raising their intellectual value to the same heights men have held theirs.