I've seen many citations of the Holocaust Museum where they say that no allegedly "Jewish fat" soap which they've tested has been found to contain human DNA.
http://72.14.203.104/search?q=cache:C8f0L_8kff8J:www.haaretz.com/hasen/spages/538996.html
That's the Israeli paper Haaretz, from Google's cache. (page is down the memory hole)
I'm no Nazi revisionist! Those bastards exterminated the entire remaining European branch of my family, as far as I've been able to research. My understanding is that the Jews in the city they were from were marched out of town and shot by Romanian Nazi partisans.
That said, it is very important that the real horros of the Nazis are exposed. Perpetuating myths only gives the revisionists ammo.
I felt viscerally sick when I looked at all the *&@^#% Nazi links that my query returned (nazis soap jews). I had to wade through a mile of sewage to find the links I found. I also found the one you located, but I kept looking, I wanted to make sure I got more than one "witness" on it.