The skull almost certainly sets limits on Bob in the skull, it outside? Whoever holds the skull controls Bob, but outside? Harry is always clear I giving Bob commands when allowed to leave the skull (Bob try’s to subvert them if unclearly phrased such as to investigate girls dorms etc.). But outside of the skull the control overBob definitely weakens, Bob was able to both break free of Cowl’s control outside of his skull and control the Ectoplasmic body of Sue in Dead best. Cowl although familiar with Bob and the skull, he clearly wasn’t fully aware of Bob’s boundaries.
The only issue is Bob summoning ectoplasm from the Never Never.either he can’t in the skull, or summoning would allow him to be tracked. Bob wanted a backup Sanctum from Harry, the obvious conclusion is that it gives him additional freedom. He is still bitching about it in The Law despite having the run of the Castle and internet access.
