The article seem to suggest that they are just going with their new games platform which supports multiple platforms. Do you have a source on it's popularity?

No, just personal experience. Nobody I know uses G+ as a social network, and I also learned a bit about the social gaming audience when I interned at a social gaming analytics company.

its a bit of a shame, because the online social gaming platform is dominated by facebook, and any small player has to play by their rules. If there is another platform with similar user numbers, facebook would have to be "better" in order to compete and the overall state of affairs would be improved.