I wish they weren't so pedantic about that. At the moment if you even mention microg in the lineage channel you get insta-banned.
As you say their hard stance is not doing them any good with Google anyway, they're ignored either way. And MicroG is a really good solution which can replace google services like cell-based location with much more privacy-sensitive alternatives. They even implemented the corona bluetooth protocol during the pandemic! The only place it uses google's services is for push notifications, necessary because most app server infrastructure doesn't have the ability to communicate with anything else. But it does so in the most privacy-sensitive way possible.
At least the good folks at https://lineage.microg.org/ provide a great fork with microg built in.