Vent blocking in Fridge freezers

Hi, my husband and I have a disagreement similar to the classic ‘toilet seat up/ down’ frustration (sorry about the crude anallogy). I insist that he put nothing on the top shelf in the line of the vent located above it because the vent needs clearance.
His view is that it’s okay to put things on the top shelf – after all that’s what it is there for – so long as you don’t WEDGE things under the vent blocking it.
After numerous incidents and altercations, he offered not to put anything directly under the vent no matter how small but would still put things at the front of the shelf even if it was in line of the vent. I insisted that there should be nothing in line with the vent from back of the fridge to the front of the fridge.

Please help!!!!! Our f/f is a Bosch integrated KIU 26444GB/01