Another classic case of European bureaucrats raiding the piggy jar of US tech companies. Like, obviously, marketplace is tied to Facebook the social network. It's how they authenticate sellers are real people and connect them to nearby people. It does a huge disservice to consumers to try to disconnect the two.
Here it deals with the fact that in that area Meta is both a platform provider and a player in said platform, and that they take advantage of the former to hamper competitors. I can't see how it's related to what you're suggesting.