Some people look good for their age and have a youthful vibe but I don’t really think that means anything.
If EVERYONE looks ten years younger then I think that just means overall we’re aging better as a society in some ways.
I was in a fitness class associated with work some years ago and a guy in it was a squaddie .
He was (allegedly) surprised at some of us in our 30’s were the age we said (me and a few others).
Tbh I think it was just that he had limited social experience and probably wasn’t used to seeing or interacting with a wide variety of women from reasonably diverse middle class backgrounds
so as we weren’t displaying “signs he associated with older women” he was guessing based on that? Or it was to do with us being in training and he didn’t really get the idea of “second careers”?
Or quite possibly he was trying to be flattering to us oldies based on the fact that he knew we were all away from home/staying in hotels and he might have been on the pull ? 
Online dating is the big one where people lie - and it’s ALWAYS obvious, even if someone has a fit body or is active or looks a certain way from certain angles or in certain photos.
There’s a lot of things that aren’t communicated honestly in terms of appearance and estimated age is one of them.
The mum of an ex-colleague of mine had been dumped for a younger woman and was on a mission to prove she could “turn back the clock” and compete with younger women
(three hour sessions at the gym, lots of appearance related stuff, eating only fruit, Botox etc)
She looked good in a way but definitely looked her age. I saw some photos of her in some “classy” cocktail bar in a fitted dress and they’re nice photos but just show a woman who looks her age with quite a “done” look.
Plus the constant “trying to start conversations about her gym interest/her appearance” meant that most people would pander to her humblebragging and offer a compliment out of politeness but not really know what else to say apart from that?
So unfortunately I suspect it then became a bit of an “emperors new clothes” situation with her thinking that she really looked 30.