LOL.
That's probably preferable compared to actually falling for it. I'd only seen a few selfies of them and saw a bust and other obviously female characteristics so I had no reason to believe this person was anything other than a woman at the time, until I met and saw them in person. Besides their voice just seeing their stride, arms/hands, waist, etc, it was a dead giveaway and I was pissed off.
I used to mass swipe-right on Tinder a while ago and 1/10th of my matches were trannies. Many of them were hilarious troglodytes and I regret not screen capping them (come to think of it, I should pick up the habit again to get some content to post), but some of them I had to squint at for a few seconds to definitively clock them. If I weren't enlightened by my degree in transphobia from Kiwi Farms I probably wouldn't have detected some of them at all, but I was like, "this head-to-torso ratio isn't right

" etc. And some of the east-asian ones still legit fool me to this day at least in photos.
There's a number of reasons why a normal person or even a transphobe with a kill-count in the billions might fail to clock a tranny:
*FaceApp is common now and not just among trannies
*basic photo-editing skills are also common nowadays. Fashion magazine-style editing of curves and proportions may be a thing
*rising obesity rates mean that you see a lot of indistinct potato people of both genders who can throw off your sense of what's normal if you look at them for too long (allegedly many parents of obese kids underestimate their kids' weight).
*increasing number of young trannies. Young men can cross-dress more successfully, again at least in photos
*A portion of mtf trannies were always gay men who are more likely to know how to do makeup and wear clothes, which is 90% of how you semi-succeed at it
(pro-tip for trannie lurkers: being on HRT for years helps 0% with passing so you may as well just cross-dress like drag queens and skip the debilitating drugs)
Of course as you say, it all falls apart when you see them in reality.