The loan is against a house that does not exist yet
A renovation loan is unusual because the value it lends against is the value *after* the work is done. The property in its current state would not support the loan, which is the whole reason the product exists.
That single fact explains most of the rules that follow. If the lender is lending against a finished house, it needs strong evidence of what finished means, and that evidence is the contractor’s scope of work and bid.