I agree, but they're swimming in disingenuous waters. Surely, they can't run 100 versions of the site to suit 100 legislative/court systems. Well, maybe Facebook can. Can tinder? What about the next Facebook?
Maybe there can be no next Facebook (as in, one multinational actor is position of monopoly on one type of service) and maybe that's not a bad thing.
If the only way to have the same kind of service from now one is to use a network of separate entities each smaller than Facebook and interoperating between themselves, it might be a good side effect of the law.
What I fear is that there is no next FB because fewer people can "enter the market" that in this case is necessarily international .. can't because you need to start with a team of lawyers and compliance officers.
FB is unlikely to get injured. They're big and rich and have a deep moat. It would take a lot to shave 5% off its revenue. Making a potential FB competitor restrict itself to a smaller market, and a more localized service... It doesn't take as much.
If lots of people can "enter the market" the one of these might succeed. FB is just an example, but I also mean them. Most of these potential fb-killers don't know that they're competitive with FB.
Think of WhatsApp (again, just an example). They entered the market, at an angle. Within a few years, they threatened FB enough to get bought, just to eliminate the threat.
The end result isn't all that heartening, but everything up to that is. I'm not saying GDPR makes this impossible, just worried about the accumulation of these things. Even a handful of reasonable rules could make things harder, especially if they are different in every country. WhatsApp might have decided to focus on a few core markets, and limited their idea to more local things.