So far as I can tell from my inventory, the beveling/feathering of the edges of the backing paper continued until the switch to a plastic backed backing paper. It was certainly still so treated when 120 switched to plastic spools in the 1970's. (The other roll film sizes used metal spools to the end.)
From the patent, I think that the paper was "distressed" before it was cut. Pretty much just run it over a flange that stretches it, and puts a dent in the paper. Then cut down the middle of the dent.