Man, that conduit was probably put in for knob and tube or an old phone line back when they actually planned ahead. Here is the thing nobody talks about though. Those old raceways are getting rare because every flipper and DIY guy rips them out during remodels. They see a pipe that does not match the new stuff and just yank it. So what you found is basically a dying breed. I have started taking pics of any old chases I find and noting them on the panel, because once they are gone they are gone. Twenty minutes versus an hour is a gift, but the real win is that path staying there for the next guy.

What was the wrong clue that sent you down that rabbit hole? Been there before and it's always some dumb little thing you skip right past. Did you end up fixing the real problem or just swap parts til it worked?

Rules like that stick because the person mattered more than the advice ever did.