Self confidence plays a role so it's a sort of self fulfilling prophecy, but there's no question others treat you differently.
Going from being ignored in nightclubs, and have people tap my shoulder if they needed to get past, to having people instead slide their hands over my pecs or stomach or pat them to get past (both men and women suddenly started doing that), getting my butt pinched half a dozen times a night, and having half a bunch of random strangers who also lifted weights want to high five me for no reason.
I'd never had women pick me up in nightclub before, as opposed to having to be the one to approach. Afterwards I did. I had random women want to make out with me within minutes of meeting on many occasions. Of course not all of that is necessarily down to the change in my appearance - it's very possible some of it was also down to my increased self confidence, but either way the difference was massive.
Looks and confidence are of course by no means the only things, but it's a multiplier, and you can up that multiplier significantly by lifting weights.
But qualitatively different attention IMHO.
Great looking guy with zero personality: shallow attention e.g. one-night stands or pure accessory.
Ugly guy with great personality: veer towards long-term relationships or maybe friend-zoning.
Actually I was talking about what I have seen in friends and acquaintances, although I have seen exceptions too.
Might depend upon country too...
The hn crowd seems to be particularly international to me - making assumptions based on SV seems wierd. I am in New Zealand with a normal ratio of genders, and plenty of social situations to meet women since we have no lockdown, however I have heard that NZ has far too many sheep.
On topic: I am acquainted with one world-competing female body-builder. She comes across as extremely competent at the other parts of her life (good artist, good at running her own business).
Granted you need to be otherwise attractive, but it’s not just women men also treat you more positively. Women see a wider range of responses, yet it’s still generally a very positive experience.