Thus Spake Zaranephilpal/SimultaniousFlurries
From Exalted - Unofficial Wiki
From the WW boards: 5/26/06 http://forums.white-wolf.com/viewtopic.php?t=39958
It's pretty clear to me that simultaneous flurries probably need to be resolved with tiering of actions in order to check for applicability.
That is to say that every action in a flurry really needs to know how the prior actions went to help check validity.
It gets sticky when you suddenly have multiple flurries going off on the same tick, for which I'd suggest that everyone's first action be treated as a simultaneous action, and then everyone's second action, and so on until you have no one else taking actions.
This is something I really should have done a better job with on the rules.
Oh well. Live and learn.