I might be misunderstanding it, but microg is not (like the name suggests) a stripped down version of the google services. It is a reimplementation of the APIs that the google services provide to installed apps. It doesn't reuse any code (it couldn't, because the google services are not open source) and doesn't connect to google servers, afaik.
As per their motto, MicroG is "A free-as-in-freedom re-implementation of Google’s proprietary Android user space apps and libraries". They absolutely do connect to Google services, just not with the proprietary Google implementation of the softwares, but with a reimplementation. I think this is very similar to NewPipe for example. Google's proprietary services, with an open source frontend.
