"A good knapper should be able to do it all anyway. Concentrating on just one material, technique, point type is limiting and defeating."
Although materials varied to a certain extent a prehistoric Native American knapper from a specific period and cultural group probably did only make one style of point. Clovis people weren't making Brewertons. So in turn, I would say to be true to the abo ways you would limit the types of material you use and concentrate on one style. I do understand that the highly migratory populations exploited a wide variety of material.
Also, I think that we have missed part of the original post. The complaint was that slab knappers COULDN'T knap a cobble or spall.
"Basically he told me that some of the most experienced knappers in the US can't even spall a rock, and begin with the process of a raw nodule and make a beautiful point from it. He threw out some names and said that these knappers can make the most beautiful points from obsidian, flint ridge, and hornstone slabs, but if you put them in front of a raw nodule they would throw their hands up not knowing where to start. Am I making any sense?"
I don't believe this to be true. So I put the question to the slab knappers can you reduce a cobble, spall or oddly shaped quarry piece?

