I despite such level of hyperbole, I would just twist all those sayings if I lived there just to mess with people: "This sushi is so non-life changing! Still worth it tho" "This kebab is not to die for, but definitely at least to suffer for!" "This shoes are the best, not like with capital B but still the best"

I 100% absolutely totally utterly agree with you. It took a bit to get used to people saying "I totally agree with you" only for that to mean that they didn't agree with me. I don't consider myself particularly blunt but in comparison I certainly come off that way.

Is there a particular reason for this becoming a cultural norm?

My country (NZ) has the opposite culture. It would be really weird to hear people talk with that much hyperbole.

I imagine that the Bay area is more than usually filled with aggressively ambitious people, projecting "fake it till you make it" success to both themselves and others. If everyone around you does the same, anything less than "perfect" makes you a loser, which conflicts with the self image you are cultivating. Therefore, everything must be as amazing as possible just to keep up with the rest. A sort of real life instagram syndrome if you will.

NZ (and other parts of the world as well, like the Nordic countries) have a similar reinforcing loop but in reverse. Excess boasting is seen as offensive, so nobody does it, so the average behavior trends towards modesty, making boasting stand out even more.

Yep, in NZ everyone would assume you were being sarcastic.

It’s an American thing.