If the curves happen to be when looking from behind, that could be okay… 
uh, I mean, right, but I agree that’s a sign of not thinking it through 
(have you seen that? 
)
How different are you talking?
I haven’t read Wayhaven, so not commenting on that— I’d say generally, the only times I’ve felt like gender-flipping characters seemed to be “more” a certain gender than another is if I’m reading code and I notice that the code uses one version of their name as the variable. Like in Slammed!, Ecstasy’s variable is ${evelyn}, so it felt like they were primarily more “Evelyn” than “Evan” 
and I had a hard time reading the character as “Evan” after having seen that.
Could also be a matter of what you attribute personality traits to. Like if someone sees a girl doing something feminine and thinks “this is what girls are like,” or if someone sees a girl doing something more masculine and thinks “that’s just what she’s like.” I think this ends up applying to gender-flipping characters… if you write a non-flipping character who is less gender-conforming, people might just think “well, that’s how that person’s characterized,” but a character written the same way who is a flipper might be interpreted as “that’s not realistic to their gender.”
I’d definitely say that’s cultural, too. When it’s considered manly and genteel, men will promenade and strut—just like French aristocrats a few centuries ago.
The giggling thing ties in with that thread @RenaB linked earlier ties in with this a lot.
Not having read Wayhaven, this makes me want to know, if it’s not a spoiler, what happened that people wanted to change 