It was not his list, it was another player. But they both play the rule the same way. It was at a convention, but the store they all play at is about 70 miles away from me so I will never go there, especially with my local GS only 3 miles from me

And I play with my friends weekely at someones house so i'm not worried about them. If they go to gencon or some other national convention then I am sure their interpretation will be corrected.

And vessery (whatever that is) is NOT in the equation.

The store and group is in Rockford Illinois.

Colonel Vessery has popped up here because his special ability is rather relevant to their way of thinking. But he's by no means a precedent for the way every ship with a FCS works.

Colonel Vessery, TIE Defender

When attacking, immediately after you roll attack dice, you may acquire a target lock on the defender if it already has a red target lock token.

So this is the only case of gaining a TL immediately after rolling that I can think of. And then the FAQ clarifies it further:

Colonel Vessery

If a friendly ship has a target lock on an enemy ship and Colonel Vessery spends his own target lock to attack that ship (for example, he spends his target lock to fire a Concussion Missile), he may immediately acquire a new target lock on that ship and spend it to reroll his attack dice.

Once again, this one is pretty tight and exclusive to Col Vessery. It states that he can gain that TL immediately after rolling his attack dice and then use it to modify the results. But there's nothing there that says this changes the sequence for the attack, or that every other ship you put FCS on is able to do this.

FCS is clearly after the attack, not during, and until you've compared results and dealt damage (if any), you haven't got to the 'after' part. Anything before that is still during.

The thing is, you could pursue this further with the TO, but it seems his head is firmly planted up his rear end, so there's not much point really.

And like you said, they're over 70 miles away and it's not likely to warrant the effort. They'll keep doing it wrong until overwhelming opinion to the contrary finally convinces them to do it right.

In the meantime, you now know the absolutely correct way it's supposed to work, and that's the main thing.