I think that sometimes (old) people use "50 years ago" to mean something longer than 50 years ago, forgetting the passage of time. Like "20 years ago" was the 80s, and "50 years ago" was the 40s.

(Which may be fine--an exaggeration--if it's not a serious work.)

It seems more likely to me that we'd tend to be much clearer about what "50 years ago" means, because it *doesn't* sound like ancient history to us, it sounds like (for Sedaris) "when I was 16".