After being approved you need to manually go to the app's identifier page in Developer Apple and enable the "Family Controls (Distribution)" capability. The capability is hidden under a separate "Additional Capabilities" tab.

Considering how we're getting close to the timeline and 1) App Store Connect still doesn't issue any warnings regarding these frameworks and 2) Apple doesn't answer any threads about it, I'm assuming they didn't think this thing through and predicting none of this will actually be applied in practice. On top of your questions, another very important thing that the docs don't mention is what exactly are you supposed to do when the frameworks in question are linked statically.