trailer hitch and bumper gap

[x5user]

I have a quick question for everybody. I dropped my car to dealer to check several things and they check my car if there's any damages. Service person check my left rear bumper as damaged because gap between bumper and body are too large.

So I told him, I have never had any accident and my bumper doesn't even have single scratch on it. He said it might be happed if someone sat on my bumper. So I said if someone sat my car it will be lower part of hatch, NOT on the bumper.

Somebody stepped up told me that gap has been created because of trailer hitch which has been installed in factory.

Here are my question.
1.Is it normal to have bigger gap between body and bumper(I noticed that gap is not even from right to left, left side has bigger gap) because of trailer hitch installed?
2.How heavy person has to be to lower the bumper to make bigger gap? ( I don't think this will never happed)

I will be appreciated any comment.