BTW, before molly supported unified push notifications, it was also using websocket and that still required to enable unrestricted use of battery, as currently conversations does. Once I the unified push molly version showed up, such unrestricted use of battery was no longer needed. Websocket definitely is much better than GCM/FCM, but it implies, I believe more battery consumption, though perhaps not unbearable.
Jami was also using websockets and required to allow consuming battery on the background as well, and then moving to unified push no longer required that, but in the case of Jami, by being peer to peer, the effect is more noticeable.
All that to say, that other apps have moved to unified push notifications for better battery savings, even though they used websockets before, and curiously enough conversations does take advantage of GCM/FCM push notifications, so is not clear to me why disregarding unified push ones, but it's always up to the developers/maintainers, and what they need/want to invest on... So that's why I mentioned I don't quite get what was mentioned on the github issue, though it was clear to me there's no intention to provide the support.