That stinks. I have to imagine it would make the bootfitter's job easier to have boot flex ratings standardized. And wouldn't it be easy to measure? Maybe in terms of force required to flex a given pair of boots forward 10cm or so?
yes it would be except that temps effect boots (some more then others)
cuff size/shape to attach something
some boots are stiffer in the front cuff, some boots are stiffer (more re-bound) from the rear spine.
different peoples ankles and boots are not at the same place, so some brands might be better biomechanically to flex.
It would be nice, but still just a starting point or goal