My impression from second and third hand sources was still that YT Music implementation and brand was after GPM was asked to "code freeze" and the team directed to other projects (including some to YTM). That the products stood side-by-side for so long is only further indictment on the rewrite-the-world approach that it took them so long to reach "feature parity" enough that they felt comfortable sunsetting GPM, well after the writing had been on the wall, the development ended, and the marketing decision to change brands had been handed down.

The multiple parallel offerings thing is of course its own problem that seems to often indicate communications issues up/down the decision chains, but specifically with reference to GPM/YTM I heard it was more a symptom of a rewrite than one of those communication breakdowns. Though again, that's only from impressions I got from scuttlebutt I heard second and third hand.