What's the reason for a piece of sheet metal keeping a full size tire from going in the spare tire well in the rear, when driving on the compact spare? It looks like things would fit if I cut the metal piece out of the way. Should I not try that?

During a recent long trip in my wife's '04 A6 Avant, loaded with luggage, one of the OE Pirelli's blew out on the interstate. (no sidewall left!) Replacing it cured a vibration that the dealer couldn't fix, but... I discovered that the OE Pirelli wouldn't fit in the spare space under the rear cargo area, and it had to replace luggage above that. I won't go into detail about doing it in a thunderstorm, which made things much worse, but what's the idea of blocking the spare tire well? (Owners manual says to put the OE wheel/tire in the cargo compartment, secured with a net. I guess I shouldn't carry luggage there.)