DeletedUser28 Because MicroG has a smaller scope of making only the "useful" connections to Google, like FCM, but not all the other connections to Google that Play Services are most probably doing. So there is some merit to having MicroG as a "light" version e.g. only for Push Notifications and nothing else.
I can suggest a better alternative. Use A DNS provider which can block domains, such as NextDNS,
or you can run something like PiHole on a VPS if you don't trust them, there are many lists, all in all
you can block Google completely, and allow only:
*.mtalk.google.com - just for FCM
*.googleapis.com - when you install apps from the sandboxed Play Store
Disable the Play Store when not in use. Use a throwaway account to download your apps.
The footprint is around 1GB for all the 3 Gapps (the only downside) but they are sandboxed and
constantly updated. If it's a throwaway account, I can't see how Google can benefit from the list of
apps they inevitably know I have installed using that account. But - all apps work, and no security issues.
If other ROMs could support sandboxed Play I'm sure they would prefer to use it over the reversed
engineered hackjob that is this microg project.