If I'm out and about sometimes I'll sit for a while in town just people watching.
My eyesight is crap these days, definitely need to make an opticians appointment, but even so I'll watch people way way off in the distance and think that's a woman, that's a man. And once they are close enough to come into focus I'm always correct.
I watched two people the other week, same height both seemed to be wearing same coloured trousers and a similar coat, both short hair etc. I'd guessed woman in the left, man on the right.
When they got close enough presentation wise there was nothing to tell them apart, they were both wearing completely identical clothes, same trainers, same jeans, same coat. Same haircut, same 5ft 6" height and build. And they were very obviously a woman on the left and a man on the right. (And as an aside I'd bet good money they'd been married 40+ years to each other!)
I don't understand why some people try to claim humans can't correctly sex other humans.
And I'm sure there will be people who will still try the "but you don't know you were correct" .
At which point all I've got in response these days is a heavy sigh, a shake of my head and to look at them in a way that conveys "you really are quite a stupid individual aren't you?" .