I agree with everything you say.
It surprised me that one of the responses I got today was it would be confiscated and I would need a FAC to get t back as it would have to be registered as an FAC gun and that it would not be able to strip it and reset it to a correct level and return. This was not even an option, this is what made me ask the above question. The cost of the work is obviously down to the owner of the gun.