i actually just looked at the sekai balance post from the developers, and 3dmvs are indeed priorized (although they make note of distinguishing comms from covers, but that's kinda obvious seeing how everyone has an even amount of 2dmvs and 3dmvs ending at the 4th rotation, and saki at 6th rotation, too)

hopefully vbs gets covers soon to complete their album. at least l/n is technically on par with the other groups (but behind in the album due to bump of chicken's songs lol), but in vbs's case not even aun no beats puts them on par with the rest😭 cover distribution currently is:

37 - mmj! & n25
36 - l/n & wxs
34 - vbs

so yeah, very behind. vbs cover spam (hopefully) incoming?

also not really related but it is worth mentioning cover distribution is also a priority but it's only by groups (which checks out, looking at mmj's full group covers total compared to other groups lol)

and 2dmvs are also prioritized, but i don't think they made a distinction between comms and covers, unlike with 3dmvs. and the vs ones don't count into rotation.