Here's the deal. The soap was sold commercially only. The soap was banned from sale in the US but not Canada. The soap was banned around 1970. That means you would be lucky to find this soap in one in a thousand homes. The book WIASC was co-written by the top detective in the case and he says all of the victims had Physohex soap residue on them.Physohex was not rare. It was banned but it was in many places and used by people. It is also a fallacy that all the kids were bathed and clinically clean. I can't produce the proof of that at this moment so you can choose to not believe me and that's ok.
Based on the fact that it was claimed by Anger that the soap was used and Punky is the OCCK it is safe to say that rumor was/is true.