We demonstrate how metal UPD may find use as a general tool to determine the collective defect area in hybrids between 2D materials (graphene, hexagonal boron nitride, etc.) and various substrate metals. By investigating copper UPD on a monolayer of hexagonal boron nitride (h-BN) on Rh(111), we explore how this process can be used to quantify the defects in the h-BN monolayer which form during its chemical vapor deposition. In addition, the UPD signature allows assessing the potential window of the h-BN/metal hybrid, which is important to explore its functionality under ambient and electrochemical conditions. Importantly, UPD itself does not alter the defect area on repeated cycling. Overpotential deposition, on the other hand, is shown to have significant consequences on the defect area. We show that this non-innocent Cu electrodeposition involves intercalation originating at initial defects, causing irreversible delamination of the h-BN layer; this effect therefore may be used for 2D material nanoengineering.