I would say it was a myth for the very simple reason that the Majority of he victims of the Gas Chambers were cremated on the spot. Making it difficult to do any rendering. Although the human hair was used for various pruposes. Male hair was used for Industral felt and thread, while female hair was used for to make Socks for U-Boat crews and flet stockings for railways (whatever the hell they are). This was not just the victims of the gas chambers but more the imates of the concentration camps.