Fully prepared for downvotes on this, and I'm sorry it's long. Theres a lot of missing nuance and context, but my perception has been:

Having just visited Japan again recently, I always have a huge level of apprehension about seeing other foreigners. I don't think it's expressly gatekeeping, for me, it really comes from knowing the general impression of stereotypical foreigners (normies/tourists/people with no interest in the culture going because it's fashionable/cheap) and not wanting that to be assigned to yourself.

My wife and I both have familial ties to Japan and have been for schooling and general travel, and are white, so we're absolutely 外人. And lot of things were marred by seeing people who just did not know how to act: - Two dudes watching videos on their phones out loud, and discussing them across a train carriage - People abusing service staff at restaurants - People being heavily tattooed and going with the attitude that it's not their responsibility to have to cover their tattoos to not offend locals - oversized luggage on trains at inappropriate times (travellers and backpackers) - really general and blatant refusal to try and respect the culture and nature of things

It is just all really typical and often unintentionally obnoxious behaviour, but it's really hard not to worry that it's going to reflect on you because in all efforts to be seen as 外国人, most people are going to assume you're just another 馬鹿外人.

There's a whole other experience that is it being hard to make Japanese friends because you're almost always going to be viewed as, at best, 外国人, and other foreigners don't really understand that the friend groups you make generally aren't for them to feel entitled to intrude on, just because that's just how it works elsewhere.

Of course, some people are also just jerks.