Apple Watch Screen Time Communication Limits

My 10-year-old kid has an Apple Watch Series 7 on watchOS 8.7 with cellular paired with his iPhone Xs on iOS 15.6.1 (because he has friends with Androids and wouldn't be able to communicate with them if we just set up the watch as a Family Watch). He currently only uses the watch and leaves the phone at home because he's less likely to lose the watch and because it's less of a distraction than the phone. After doing some browsing on the forums, it appears that while I can limit his communication to Contacts Only on his phone, this does not then apply to the settings on his Apple Watch, so he can send/receive calls and messages from anyone on the watch. How do I apply the communication limits to the Apple Watch, and if this is not currently possible, what is Apple doing to fix it?