finderI mean it's a fair question. For a long time, Lang and Rossignol used the exact same molds for their shells. No idea if it's still that way, but it's not unlike manufacturers to share molds across related brands. Another thing to consider is that most ski boots are made in the same part of Italy. Totally agree that "the one that fits" is always the best option, but I see a valid concern that someone may want to avoid a shape that does not fit, which very well could be implemented across the board.
I completely understand the OP's question and you have a valid point. If i couldnt find my size in a Rossi BC130, i would just go buy the Lange RX130. Hell, even Nordica to this day will tell you that Blizzard and Nordica have separate R&D for their skis.. have you ever looked at them side by side.. they are basically the same skis.. A rep even went as far as to say they built the facility with "a physical wall between the two"..
K2 and Line are starting to share more tech as well. Line's THC in the Vision and the K2 Mindbender.. hmm....
I've put on the Mach 1 and the Promachine. The Mach 1 did not fit as well as the Promachine