Unless I'm misunderstanding what you're trying to say, just because we do not observe it doesnt mean server side it runs a QA/TA/DA check on the attack round.
Byrth said he OHKOed 5 rabbits in a row on thf without having gil deducted, then the 6th deducted gil. The only logical explanation is the first 5 rabbits were OHKOed by an attack round that proced triple attack (even though the second and third attacks never happened), the 6th rabbit was not a TA attack round.
I think you're totally misunderstanding what I'm trying to say (and I think we agree).
It makes sense that the server decides how many attacks before the round starts. (although I did not really think about this)
It was not intuitive/obvious to me that gil is deducted when the round starts (rather than the actual swing - which would never happen)
The nominal test for this is pretty simple: 0 multi attack on a job, check gil, use item, kill something in 1 hit, check gil (1k less) (which is all I initially was describing - so it was a bit of an indirect response I guess)
Go forward from their with other tests (TA vs. DA vs native DA etc...) which make more sense now, I just misunderstood the initial premise since its more intuitive to observe the attacks. (those results are clear as a bell after clearing up the initial mis-intuitiion)