I was fighting Cactuar Jack a few days ago and noticed that I was able to interrupt some TP moves using Flashfreeze II. I mean, mob readies Sun Spine > Flashfreeze II > Got "Cactuar Jack's legs are incapacitated" (or something similar; I can't remember the exact message) > Sun Spine fails and the sabotender don't jump THAT TIME.
Anyways, we're gettin' battle system changes, so for me there's no need to worry much about this WS mechanic. I'll check it out by the time battle system changes arrive, that's for sure.

PS/Off topic: What's the cubic status icon when you incapacitate a mob using Flashfreeze II?