You are correct that lower tire pressures are desirable in certain conditions, but the reason for this has more to do with control, not pinch flatting. To reduce the possibility of pinch flats, the pro mechanics put on wider tires, which hold a greater volume of air. The wider tire permits them to run lower tire pressures. So, to get both control and a lower possibility of flats, they go with a wider tire using lower pressure. To further enhance control and shock absorbtion, they also use a different wheel (commonly 3 cross, 32 spoke).


On really rough surfaces like cobbles, one reason pro mechanics lower the tire pressure is so that the tires don't bounce needlessy off the road surface which reduces control ( you can't control a tire with brakes or steering that is in mid-air). I mentioned higher tire pressure with the narrower 700X23 tires in my post since with this narrower size which is suitable for normal road conditions, there is a higher probability of pinch flats since the volume of air the tire holds is smaller, hence less margin for error due to the reduced ability of the narrower tire to absorb the type of shock that would cause a pinch flat.

In the Tour de France this year, the Phonak team had something like 7 flats in the team time trail because they were using 700x19 Conti track tires in adverse weather conditions.U.S. Postal used wider tires and avoided flats but still posted the fastest time. If you watched the TTT, at the end of this stage, they showed and commented on some of the narrower tires bouncing off the cobblestones that were present as the riders approached the finish line.