The first SX90s were built without the external bar but the 'cuff' was very susceptible to being cut from ski edges.Maybe it was an option, and my ski shop figured the stiffener made sense for the equippe level and pre-configured them that way.
There was a retrofit of a plate covered with a kind of think black primer type paint. It wrapped slightly round the edge of the cuff. Came with 2 small self tapping screws. Seem to remember that there was a metal plate in the cuff that you drilled into.
The ver 2 was riveted onto the cuff at the factory - a plate with two slightly raised strips fore and aft.
The boot in the pic is not from the first iteration, I think it's season 2 onward tho it could be that the design changed mid season.
Ver 1 is on the left