I think a lot of these are in the ANSI 2016 spec. I haven't looked at the older specs, maybe they were simpler.

Eg here is the `a+1` vs `1+a` thing explained for ORDER BY - https://i.imgur.com/bklpjkP.png. Here are the conditions under which ORDER BY can reach inside SELECT to pick columns from the FROM clause - https://i.imgur.com/aoeqDGn.png.

Chapter 2 of the spec is 1732 pages of that kind of language, so it's hard to be sure that any particular behaviour is not in there somewhere. But I'm fairly sure that all the examples with set-valued functions are postgres-isms.