As long as micro G is a system app in my opinion it is the same why not run it as a sandboxed app. There is probably a reason why it can’t just think it would be more privacy first approach to sandbox it but that is just my opinion everyone’s threat model is different I don’t use Google at all anymore so non issue for me. Still better than stock Google Play true just think micro G could do more.
I use this on my pixel with Graphene OS and it works great once I completely degoogoled my entire phone my spam calls and text pretty much all went away.