The API of Google Play Services is not really open to re-implementation by third parties. The fact that microG exists doesn't invalidate the author's point. Goo

The API of Google Play Services is not really open to re-implementation by third parties. The fact that microG exists doesn't invalidate the author's point. Google allows microG to exist because it is something of a niche, it is not threatening to their model. The second point you are trying to make is not really clear.