And here I thought I had covered the bases on the FAQ's. I don't know what your friend is on, but I would like some of it. Shoulder holsters ARE NOT illegal.
I'd be laughing harder over this, but it's kinda sad too... Good to check on though.
The only illegal holsters are ones that completely conceal a gun and allow it to be operated. The BATFE has decided those are "Any Other Weapons" as they allow a gun to function and no longer resemble a gun. An example would be some types of wallet holsters.