I suspect you are correct. I think Google wants G+ to be a useful way for people to find people they know, as that is the sole reason many people are on Facebook.
I think it has more to do with Facebook and Microsoft taking away quite significant parts of the online ad revenue. Facebook is economically destroying Google in terms of display ads.
Companies don't have loyalties to either company, they just go where the best value is. Currently thats Facebook.
Google developed an attention economy, and Facebook has improved it.
