My experience proves otherwise. Every time I see a dow, the relation meter has reached hostile by several issues (wants provinces bla bla bla), granted eventually it will result in the same reaction, but there is a build up of reasons in it. Relations is one of them.
My experiences have indicated that the only thing that stops a nation from declaring on you is allying them. Putting that aside, the AI then looks through all possible targets it can declare on that it isn't allied to, determines the ease of the war vs the cost of the provinces it wants, determines the ease:cost ratio, and then goes for it. This is why hostile core creation cost serves as a deterrent for being declared on, to a degree. So basically, things like army size, hostile core creation cost modifiers, and alliance webs serve as much bigger deterrents than relations do, so long as you're not allied to them. A -10 modifier does not affect this in the slightest.
Also, do me a favor and don't attribute things I didn't say to me. I'm pretty sure it was an honest mistake, so I don't hold it against you, but it just looks weird when I see you attribute a quote to me and I scroll up one post and see it said by someone else instead.
Edit:
EDIT2: And ofc I over wrote the save game....Anyway what I wanted to post was this: I released an OPM from Quara Quiowhatever (lets call them the mustard horde ok?). Immediately after, the mustards form a coalition that is been Joined by the Mams, Lithuania (!?!?!?!!?) and the little OPM. So yes they do join.
This is due to a bug in the game's clearing of relation modifiers when a nation gets annexed, though. Often times, when a nation is annexed, only about half the modifiers are removed instead of all of them. As a result, if that nation returns to the map later in the game, it's very possible for that nation to still have AE from when it was still alive.