History Channel used some bad physics on air and I came here to rant about it

Ok, so on the History Channel they are trying to figure out how the Incas moved these massive stones. So the guy starts off by saying, "to make the stones easier to move, they made the bottoms concave inwards, to reduce the surface area in contact with the ground".

Then the guy went on to put a concave piece of metal attached to the bottom of a cinder block and pulled it through some gravel, then said "to pull this 17 pound block, it only took 8 pounds of force, therefor the concave bottom allows one to pull a stoned with a force equal to half it weight, therefore the Incas needed x people to pull a 2 ton stone because each person can pull x pounds etc.."

First off, I thought the coefficient of friction was independent of surface area? And the amount of frictional force needed to be overcame in order to pull the block is based off of the coefficient of friction.

Secondly, he used a piece of sheet metal attached to the cinder block to provide the curved bottom, this completely changes the coefficient of friction and throws off the theory.

then they go and make a giant conclusion at x1000 scale .. end rant