Notifications apparently do go out for backdated fic, because I got notifications for all three of these!

I wouldn't call it unwanted, though; I subscribe to a bunch of people, and not all of them are exclusively into fandoms I care about, and I'm perfectly fine with deleting a notification if it's for a fic that doesn't look to be up my alley or that looks as if it'll be incomprehensible because I don't know the fandom. (That said, I like SG:A. So!)