> Fortnite could have chosen a different game engine at the start (this is not about terms changing after all)

Right. Apple's terms were clear from the start, so Fortnite had no reasonable expectation to be allowed to violate them. Just like Fortnite could have chosen to use a different game engine if they didn't like the terms of a particular game engine, they could choose to focus on non-Apple platforms (or choose to abide by Apple's terms on Apple's platform) if they don't like Apple's terms. I'm not sure what you're getting at.