how about head and seat angles, as well ? Or seat post diameter

Realistically, I do not trust most sellers (on ebay or CL) to know how to measure a bike. Most (non-flipper) sellers (and a good amount of flippers) see a bike like something that needs to be sold, like a used window airconditioner or something that takes space. Unless they are enthusiasts. And in that case, expect higher prices.

Here is what I do: If I am to buy a bike for personal use from a CL ad, I always bring a measuring tape, and take it from there. If it is an ebay bike (and I bought just one bike and one frameset on ebay for personal use) I figure out the size and then I look up the charts, or base it on personal experience by eyeballing it. If it is a bike I do not intend to keep, I assume that it will not fit me and if it does, it is a bonus.