All this is because google never wanted to block, if google decided to block.
I looked at the legal framework which governs all this. Google can update software very fast, but google cannot update legal framework fast, it will take years.
There is no reason for google to block, in fact, making it work is very important. Google already made a provision for China phone and Custom ROM phone to access google play services, means Google bless this.
The contract of google play store, google mobile services and google services framework, is all centered around a direct relationship between google and the user. Google cannot block this.
The GSF number I don't think they can center it around one brand, and however it's hashed, the private key (sorry for loose use of this word, I am not crypto guy) identifier is for `who is certified' and not `who is not certified'.
So I can't think of a technical way for Google to ban just one brand. He can however ban everything but then it is such a huge disruption.

