That makes no sense. Because the AI doesn't do it, it's considered cheese? The player should be as dumb as the AI?
1. It is cheesy, because it uses a flaw of the game. If you don't want to be called into offensive wars then uncheck it via favours screen. The result will be the same and yet you don't get favours. That's the cheesy part.
It is obvious that the game is not supposed to allow it, but a player might take advantage of it.
2. The fact that AI doesn't do it is not the reason. I just answered your question. If you want some "fair" number of countries to set as friendly then you can aim for the number AI countries set.
3. Player can do whatever he wants. It is his game. I don't mind if he goes to the gamefiles and disables AI to do a WC on Easy mode as Ottomans. I am against the idea of this thread for one clear reason:
-To me this tactic is cheesy, I agree with people who say that the
very option to do that should be changed by Paradox, and the author just asks if it could be done automatically. What next? Maybe the game should make safescums on Ironman.