It's a feature that can be implemented, with similar if not better effectiveness, in various ways that doesn't completely lock down a platform. Don't ask me how because I'm no match for brains at Apple but if EU succeeds in forcing Apple to open things up, Apple will rise to the challenge and will figure it out, just the same way they figure out how to roll out an ECG monitor that complies with local regulations of multiple countries. In other words, Apple already works under large amount of constraints of existing laws and regulations when creating products and that requires a lot of constant innovation in itself. This will just be another constraint they have to follow.