not so much the "deck" height but the flange on top of the holder, thinner would allow the case to be pushed up farther into the die yes? and would that not allow the case to be sized a bit farther down?.
all other things considered the case seems to fit the shell holder perfect no alignment problems at all.
it's not that big of a deal its only a 8 dollar piece it just got me over thinking it I guess.
off to the store...Matt.