...And it would be equally bullshit to encounter someone missing a finger and start berating them. "You don't really have four fingers, biologically you're still five-fingered!"
It's appropriate to discuss generalities. It's appropriate to discuss individual cases. What is inappropriate is dismissing individual cases to come to a general conclusion, and then insist that it applies universally.
No it's appropriate to dismiss individual cases to come to general conclusions. We do this all the time with outliers. That's how we classify large sets of data. Classifications are very useful and should not be thrown away. That said you treat an individual as who they are not with generalizations. You don't say to a six fingered individual you're five fingered. But if you want to make gloves for a living you're going to sell more volume if you make five fingered gloves.
This is also in the context of trans people the vast majority are not biological outliers simply people identifying as something different to their unambiguous biological sex.
> the vast majority are not biological outliers simply people identifying as something different to their unambiguous biological sex
To make this claim, you would have had to find an exhaustive list of biological sex differences, and check a large representative random sample of transgender individuals to see whether all of those biological sex traits aligned "unambiguous[ly]" with their assigned birth sex.
Since I am quite confident that this work has not been done, may I suggest deferring to individual people to tell you what is going on in their bodies? While imperfect, self-reporting is still epistemologically far superior to you just pulling this claim out of your ass.
It's appropriate to discuss generalities. It's appropriate to discuss individual cases. What is inappropriate is dismissing individual cases to come to a general conclusion, and then insist that it applies universally.