'There are many ways to deal with this type of backing.'
Could there be two completely different versions of R-100? The anti-halation layer in the R-100 I've used was definitely not a backing - it was an interlayer between the emulsion and the base. It behaves very differently from the carbon rem-jet AH backing I'm used to, for example. It's less dense, apart from other physical properties - it doesn't look as much like an AH layer. I've never developed R-100 to a neg though. (Rem-jet, or the Fuji equivalent, is used on all current colour neg motion picture film as far as I know, and Kodachrome - though I've never processed Kodachrome!)