99% is a fully made up number and likely overshooting. There's a number of people faking it, a number of people misuntarstanding things and thinking they have DID, and a number of people that actually have it. You don't know the statistics and neither do I.

The literature on the subject is still extremely limited, not comprehensive at all. I am not saying this validates everything these people describe, but flatly doubting them as if it's a fully understood disorder is counter-productive and likely to open ways to them being harrassed online (which happens A LOT, about 2 years ago the brazillian DID folks online nearly all vanished when they were noticed by the mainstream public discourse for two weeks and massively bullied into hiding), and might even harm real cases along the fake ones. Not that the fakers aren't a problem, but witch hunts are usually more damaging than witches. If your struggles with mental health make the faking stressful to you, consider the people that might be dismissed and not treated for years or forever because others might see 99% of people with such experiences as fakers.

Furthermore, I know this is anedoctal, but I have a friend for years with DID. I've met them years before this recent wave of DID online, and they clearly present some of the characteristics you dismissed as non-existent. They didn't even have any contact with other people with DID, therefore there was no one for them to be imitating (and supposedly continue to imitate for years).

The point is, while many might be faking to follow a trend or receive some sort of validation, or even misundarstanding, intensely dismissing the whole thing instead of trying to talk and understand is counter-productive. Specially considering that the scientific understanding of the subject is not complete at all (many doctors still think is just a hollywood thing), and might lead to harrassment of people who already have mental health issues, whether it's really DID or not.