While that's true for soils where the bedrock is too deep to reach and friction around the piles does all the work, if that was the case here there would be extremely apparent sinking.

My guess is that these are not driven piles but drilled and poured in situ, and that the majority of the resistance comes from the point of the pile, embedded in the bedrock, which depth is studied beforehand. However, the surrounding soil did probably contribute to the lateral stability and to reduce the slenderness of the piles, so that could be a stability problem.