I think Weasel had it spot-on on the first page of this thread.
She pointed out that men don't wold whistle for the woman, but for the other men they are with. It's not really about affirming or appreciating the woman, but showing off and gaining status for themselves in front of their mates, like cocking their legs in front of other dogs.
I think this is absolutely true and few men wolf whistle or do these things when alone. It is about saying something about themselves to their mates or about their ability to have control over women.
Regarding different ages reacting differently, I think in the past when society was more openly sexist, women learned to accept it and even like it and that was part of the sexist misogynistic culture - expecting that kind of behaviour, even if it wasn't welcomed, expecting or accepting that somehow a man in a group of mates could shout a sexist or sexual or personal remark in a public place, that they had zero control of. And some would have said it was flattering because society told these women that such comments were normal or to be encouraged. Those who did t like it were labelled prudes or bores or ugly - so by not going along with the culture, you were somehow the bad or boring or ugly one. And women themselves reinforced that.
When older women say they would now be flattered and haven't had anyone whistle for years, if it really happened, they'd probably feel awkward or it was intended to be offensive. What inthinknoldernwomen mean when they say this, is that they miss feeling like a sexual being and can feel invisible. They appreciate it if they are noticed or seen as a woman, but that doesn't mean a stranger with a group of mates shouting in a public place in a way out of their control, but in a situation where a loved one or someone they meet and are interested in shows appreciation of them in that way.
People often say the best response is to laugh. In practical terms, in terms of moving on quickly, it sadly often is the easiest and quickest response. Because what laughing or playing along does it to affirm what the man has just done and say it is 'okay'. It is colluding in what has just happened. Being angry or silent or whatever instead shows dislike and challenges the behaviour to one degree or another and that in itself probably provokes a response from the men or even women - comments about them being miserable or prudish or about personal appearance in a negative way - so the unwanted encounter is extended and made even more awkward. And the encounter is nest ended, because the man is with his mates and any challenge or loss of status needs to be fought back against. SPeaking up is probably what's needed but I can see why women want to just move on quickly.
What's a good response? It's difficult, but I've sometimes just said 'would you be thrilled to know your 14 year old daughter had been made to feel awkward like I just have by someone making comments like yours?' And I've often smiled and just carried on.