if a stranger tells you they're from texas, you would probably believe them.
unless you are uncommonly paranoid, you dont assume every person you meet is lying to you about who they are. you arent doing sherlock holmes-ass detective work to find reasons to mistrust their motives in giving you simple facts about themself.
even if you knew their car had massachusetts plates, even if they didnt have a texas accent, you would not assume that this random person is lying to you about a morally neutral fact. Depending on where you are, its a fact that might actually lower this person's social capital due to anti-south/anti-texan sentiments, which makes it even more absurd to assume they are lying about it. there is a very reasonable and incredibly easy explanation for why they no longer have texas plates (they moved, a thing you already can surmise), and it would be obviously rude to ask them needling questions about it to find out if they are really from texas, because it communicates a level of suspicion and mistrust that is downright dehumanizing.
given that trust is the default, the only reason you might doubt someone's self-description as a texan or any other neutral fact they tell you about themselves is if you were bigoted towards people like them and saw them as inherently untrustworthy. in my example, if the stranger telling you they are from texas is a person of color and you are bigoted and have a pre-concieved innaccurate idea of what kinds of people do and don't live in texas, you may doubt their self-description and find reasons to be suspicious and imagine they are lying about it. I will repeat: this is dehumanizing bigoted behavior. 2nd generation immigrants in the US, particularly people of color, have at length reported exhaustion with the "but where are you really from?" question. due to people around them being racist, they are not taken at their word, not trusted, when they say "I'm from Texas" or "I'm from Ohio" or any other place in the US, despite being born in the US and saying as such.
if we accept the thesis that not trusting people's self-described identities is dehumanizing and bigoted, then we must accept gender self-description as the only viable and equitable way forward. if you see someone you think is trans, or if a trans person is out in such a way as to you knowing that they are, and your immediate reaction is to doubt whether they are "really" trans or just pretending to be a different gender, you are treating them with a lower level of trust than you afford to other complete strangers. it means you see people who's gender presentation does not match what you think are the appropriate ranges for a cisgender body of that gender as inherently untrustworthy liars. any requirement that we must prove we are the genders we say we are is by its nature assuming we are more apt to lying than the general population, so pathological that we cant even be trusted to give the most basic facts about ourselves accurately.
