I use "about the same", thanks to a friend. I love the reactions (from Americans, where everyone is expected is to say "Great" or "Good" or something similarly positive).

Yeah, this is something I had to learn over my teenage/early 20s years. "How are you?" Is often not a question but just a generic greeting like "Hello" or "Nice to meet you". Sometimes it is though, but that's just one of the many examples of unwritten rules about how to tell whether someone literally means what they're saying or if there's a better way to interpret it.

Having only lived in the US, I don't have nearly enough firsthand experience with other cultures for me to be the one to comment on them, but I suspect that every culture has some things like this where the actual intent of the communication isn't direct. I suspect that if people in tech were asked to identify which cultures they considered to be the most direct in their communication, American culture probably wouldn't be ranked first. Generally the stereotypes of other cultures that are perceived as more direct get described in more pejorative terms like "blunt" though.

The greeting is generally in the waiting room. I’d do exactly the same if I was them.

> that’s an example of a fixed answer to a fixed question.

That's my whole point! The expected answer seems pretty obvious to you, given the context, doesn't it? Why then are you surprised that a different culture has an equally obvious (to them) fixed answer ("Yes") to any question asked by someone with power/authority to their lesser? Both depend on mutual learned cultural awareness, and can fail spectacularly in cross-cultural contexts.

Edit: my regional favorite is "We should meet for lunch some time" which just means "I'm heading out now", but you have to decode the meaning from the nature of the relationship, passive voice usage, and the lack of temporal specificity.

They're called phatic expressions.