Yeah, it's a bit like Fett's U.S. divers belt (black belt with wide buckle) - its a functional part of the costume in both movies, and is sort-of visible in ESB in a few places, but its clearly visible in ROTJ most of the time, so its associated with the ROTJ version of the costume, not ESB.
I said that partly out of frustration that HT gave us their ROTJ reveal/split helmet just glued together, rather than a "clean" helmet like it should be for ESB. It bugs me that it has such obvious breaks/bumps in the tusk rails, the helmet brace greeblies are visible all the time from the front (totally incorrect for ESB and ROTJ) and that the fact its two halves glued together (with a slight mismatch/seam) makes the mouth too big, etc. They shouldn't have done that with such an expensive figure.