They're going to have to make sure the firearm matches the one they're supposed to be getting...make sure it's the right model, serial number, etc. No real reason to open it before the customer gets there or to open it themselves that I know of, just a reason to look at it and make sure it is what it is supposed to be. "Inspection" implies checking it for operation, condition, etc. Unless that was part of the deal, the FFL would just look at it and make sure it's the right gun they're logging in.
