Unfortunately there's no data available publicly. Its just a good hunch on my part which is why i call it a "fan theory".
IMO, Zarb is designed for indigenous production because in a war time, the C-602 rounds will be spent very quickly. It is critical to have the capability to provide more missiles to the Navy. Zarb is meant to do that.
As for the range, i believe that the Navy is looking for multiple systems with different ranges. Its not clear if Babur-WSII will be adopted as a coastal defense system. If it does, then it would provide a longer range option to deter large surface vessels and C-602/Zarb would form another layer of the coastal defense network.
If Babur-WSII is not deployed in this role, then Zarb is all we got.