It's also an accountability issue. If you create something in GIMP or whatever everyone agrees that you did that and are responsible for any copyright issues or defamation or whatever else arises from that work. That becomes fuzzier when people start saying "Grok made this!" Especially because Grok does operate according to a model that can and does go beyond whatever it's been instructed to do, so you might be able to plausibly argue that if you craft the prompt right.

And I can guarantee that the cesspool formerly known as Twitter will try to play whichever side of that is more advantageous to them. Copyright infringement? That's on the user. Unique IP? Well, Grok had a profound and independent creative role and so we deserve a piece.