Double check the rubber spacers on the inside of the trunk. Sometimes those are not put in properly or lop sided and it causes the trunk not to close properly or look like it is sealed.

 

Another thing may be that sea's car is black. Therefore the space is much less noticeable

 

I think those guys are right and that photos won't be sufficient for you to prove your point.

BUT...after reading your thread I went to check out my P5's rear end; there is a noticeable space between the bottom of the hatch and the deck/bumper top, even when closed correctly.

It is enough that you would possibly question the body shop's job when you see it...