From places that have tried to implement bathroom bills, like North Carolina, there are countless reports of cis women being kicked out of public facilities for being read as trans, and this has even gone as far as a cis woman grandmother being sent to a men’s prison.
One common response when it’s pointed out that you can’t always tell is “well we can tell 99% of the time”, or some other high percentage pulled out of nowhere. This is a clear overestimate of how often someone can tell, but let’s charitably assume that that number is true for a moment and do some maths. If you could tell who was trans or not 99% of the time, that would still lead to nearly two thirds of the people you read as trans actually being cis.
https://katymontgomerie.medium.com/no-you-cant-always-tell-a5967cc55761