though even before the rise of unitaries you'd still have discontinuties, eg Devon and Cornwall Police being accountable to two county councils (before Plymouth and Torbay split off). Then there's the weirdness where some PCCs are also responsible for the local fire brigade too.Roughly speaking, this is what used to happen. When the geographical areas of police constabularies coincided with local authority boundaries it worked quite well. Over time, that one to one match has been lost with the piecemeal creation of unitary authorities. This resulted in committees with representatives of multiple authorities, giving unclear lines of accountability for the police precepts on council tax bills.
That said, very little about English local governance makes sense, it's all just layer upon layer of bodgery and arbitrary decision making (nothing says that more than the whole "city status" nonsense) - but that's for another thread.