In fact it is very inconsistant, although it may not seem to be at first, the snow left under the tent will actually keep the tent warmer and will make your night more comfortable.
Snow acts as insulation from the cold ground and as cushioning. Think of it this way, would you insulate a house everywhere except under the floor? No because that would cause you to lose heat. Sleeping directly on the ground ( even in a tent) will cause you to lose heat also. Plus who knows what that snow is cushioning you from. This works on the same principle as building a leaf bed, you want to lay on leaves and cover yourself with leaves to get the full effect of heat retention.
Packing the snow then piling it up around the tent is the best option (but you say it's too cold to pack the snow), short of that just put it up on the snow then pile snow on the tent. This will give you the most insulation.
Well, now you've got my opinion...and trust it is worth exactly what you paid for it
David