this is just a little mental exercise I thought of, putting a hypothetical situation that shouldn't ever matter but seeing how it works.
so the imperial list has kenkirk at ps6, and vessory at ps6. Kenkirk has Vader, and a tl on rebel x-wing A. Now the kenkirk only has 2 hp left, and has to kill the x-wing, so he uses Vader but forgot to fire vessory first. So kenkirk will die, but the question is does he die after vessory shoots, as they are both at the same PS.
what made me think of the situation is that simultaneous fire, if a rebel ps6 shot, had iniative and killed kenkirk, vessory still gets his tl ability since the shuttle gets to shoot back, but without that rebel pilot is vessory out of luck?