There aren’t two different sets of rules. There’s the simple model that’s commonly understood and taught to kids, and there’s the real world where you have context and the dynamics of a conversation and years of experience with communication. One is well defined, the other isn’t.
Them asking me to solve the arithmetic problem is condescending, yes.
My response didn’t say “anyone who disagrees with the convention is stupid.” Here’s condescension for you: please don’t make your reading level my problem. What I said was, there’s an unambiguous way to parse the expression according to the commonly understood order of operations, but it is atypical to pay that much attention to the order of operations in practice. If you think that’s a value judgment, that’s on you-- I was very clear in my example about capitalization, “strictly adhering to the conventional order of operations” is something reasonable people often just don’t care about.