I guess in theory it is counterproductive to prepoo on clarifying days...It makes sense, however I still do and my hair has no problems. I am someone who does use cones. Actually my prepoo is my DC. I do it on dry hair with heat so that it can better penetrate. Therefore, I don't believe that it is ineffective and a waste of time because the poo is washing away the buildup on the surface and the DC has penetrated beneath the surface. I am not so totally well-versed on the subject, but I know as a novice scientist that science is based upon theories, which are well-developed explanations that have not been misproven. This is different than a truth. On LHCF, we have theories, and though they are universal, they are not absolute. Every one's hair is different. As I said before, I can totally see why someone would think that it would be true, in fact it should be for most people, however for me, it's not. It's all relative.
I hope I make sense.