“Compatible” package versions is a headache to be sure… I agree that for tightly coupled ones they should be kept the same (so does rails and so we do at shoes).
If the use case is more of a plugin nature, aka I have one main library and different libraries that support its functionality I think different versioning is fine. Hope/goal being that the API between them becomes stable enough so that they don’t need to be updated just because (like it is often in rails with lots of gems being updated to a new version with no changes).
I.e. that’s what I try to do with benchee, there is a core library and the rest of them are plugins. Sometimes there need to be releases together as pre 1.0 breaking changes occur. Sometimes releases occur together because I want the new features from benchee “core” - the long term plan however is that they can evolve rather freely and independently in a 1.x world 
