I've seen this done before and I'm not sure how safe it is. Maybe if it were those blue block pallets. Also, they could have slid the tandems all the way up to take as much weight off the nose as possible. I understand that the trailer is surely empty, but still, I would think they would want the least amount of weight possible to be being held up by wood.
Those blue blocks suck, I hate stacking those, we use plastic pallets mostly, when i go to the prisons and they put 3000lbs on a pallet, I always hope its a blue one, I have had them chain a regular pallet with all that weight and had the pallet fall apart, then I really get pissed.
The blue block pallets seem to be the strongest pallets out there, but it seems like pallet jacks get tripped up on the a lot more than regular pallets.
I really liked the plastic pallets that Pepsi had. I wonder if they are the type you use at Sysco. You don't have to worry about nails and broken wood, and they were pretty much perfectly flat. They were strong too, since obviously pop is heavy and I never saw one bend or break.