Agree!Yep, these so called "private purchased" ones were often made in Ghettos or companies from GG by force labourers. It is easy to trace items made for example at Litzmannstadt (for example late war production Knocked sack's with these markings.
At some fabric mills fabrics for LW and KM were produced with a blend of human hair which mills obtain directly from Birkenau.
Agree about the CC/KZ fact, however they did not invent this process… Unfortunately, sadly ,they contributed.Pilot it is interesting regarding pre-war human hair usage as a fabric fibers. I was aware about few fabric mills which manufactured that kind of blend under RZM associated companies - where mostly the source of hair was always from KZ.