Could be that it’s only publishing to a hardcoded set of relays instead of using the user’s NIP65 relay set.

Yeah, this is sort of what I imagined it was. While we're on the subject, I think I'm ready to better understand some of the technicals of how nostr stuff works. Is there a best place to educate oneself on this? I know I could be more specific, but figure I'd just ask the basic question and see what you suggest as a starting point. If I get further along, maybe I'd have some useful follow-ups. I just want to better understand some basics of events and their components (the most common ones; for example here there is a mention of r-tags, which I don't know a thing about), and how relays works in a bit more detail. I don't know enough to frame it better than that for now.