OnePlus said that they are actively merging both platforms Oxygen OS & Hydrogen OS into one combined platform, with 3.5 being the backbone of their future efforts. This is the reason these Community builds were required.
The main benefit of combining our team resources is to speed up software updates. We know we have some room to continue improving there, and this is an important step in the right direction.
Oxygen OS & Hydrogen OS Community Builds
With the community build we are experimenting with new ideas and features, and then using the feedback from our community to refine… In fact, the next versions of the community build will address a lot of the feedback we have already received.
So we could expect a faster and more customized stable ROMS for Oneplus Devices.