The GPL doesn’t say you have to contribute anything other than the changes you make. If automattic is not happy with the terms of the GPL they should have picked something else. But then the product wouldn’t be so popular.
Honestly, I don’t see the difference from buying managed service for a software from a random cloud provider. You can go anywhere and get a fully managed postgresql, kubernetes and so many others, most of them probably dont contribute much.
It’s been debated to death in the thread linked below. I tend to fall on the side of the nominative fair use, but that’s for lawyer and judge to sort out because I’m neither.
A cursory check of law review tells me the US doesn’t have a uniform nominative fair use test applicable to the resell of goods and that the supreme court has refused to endorse a test creating a lot of inconsistency between circuit court. So everyone in that thread probably right in a different circuit court.