I don't buy into that and that isn't what the disclaimer is currently stating. Reserves the right to reassign FP+ in the event of operation...not reassign to an equivalent type of FP+
They also reserve the right to not honor the fastpasses at all, just as airlines reserve the right to turn off their frequent flyer programs and not give you anything for your miles. But none of those things will happen except in truly terrible situations, in which case, I expect that there will be even bigger problems to complain about.