It sounds like they were intentionally trying to reproduce the look and feel of the old style tux approach where an actual cardboard or supremely starched white collar piece (or full dickey) was worn on top of the cotton shirt. Some of these were referred to as "boiled shirts" because they were so supersaturated with starch that they had to be boiled first to remove enough starch to wash the shirt properly, and some were made of a material that was literally laminated onto cardboard to keep it rigid. Have you seen the old Bugs Bunny cartoon where the opera singer's cardboard dickey goes flapping up out from under his belt?
Now Sideshow wouldn't just use cardboard to be cheap--they had a reason for it and I think they were trying to approximate the look and feel (and in some cases the actual materials) of an antiquated approach to tuxedo tailoring. Notice that none of the contemporary Bond PFs have gone this route--they know how to make a 1:4 scale tux, and in this case it is a specific period look and feel that they were trying to reproduce in scale, and they weren't just being cheap. However, I can certainly sympathize with those who don't like the approach. But they were probably limited in options when it came time to find a cardboard-starched equivalent in this smaller size that would give the appropriate rigidity.