Well, on your logic, the pilots engaged a target without the FAC allocating it. The FAC never cleared them hot on the Brits, and the first he knew they were engaging was their "rolling in" call. If the CAS mode required them to get permission to engage, then the A-10 pilots screwed up. If not, then the A-10 pilots were the ones who made the identification, not the FAC, and they were the ones who screwed up.
There are all kinds of accusations flying around (the Sun "expert" misinterprets every shred of detail to make these pilots look really bad.)
Rule #1 is "if you're not sure of the target, don't drop or fire on it."
They weren't sure of the target. That's evident. Yet they fired on it, anyway. Was theirs a criminal act? Frankly, I don't see what sending them to jail would do for anybody.
Now, why it happened is interesting: with the ANGLICO, they are adjusting fire on an artillery target (vehicles in revetments), that is different from the CAS target they spot. The ANGLICO is occupied with this process: he's in comms with the firing battery processing an adjust fire (NORTH 800) and getting an accurate timing so he can have the A-10s observe.
The pilots spot the "new target", and suspect it's friendly. At this point, things go askew. The pilots are fixating on the "4 or 5 evenly spaced vehicles", while the ANGLICO is heads down with a fire mission.
Rather than accurately call out the new target, the pilots prejudice the ANGLICO's answer, asking something like "There aren't any friendlies this far up North, are there?"
They are now talking at cross-purposes.
Whether the ANGLICO had accurate target information or not, he's focusing on plotting a target considerably north of where the pilots are looking. So even if he knew about the recce column, he wouldn't give a response concerning it.
Things now get bad, as the ANGLICO and the pilots step on each other trying to get information on their separate tasks. The pilots do not ask about seeing orange, but rather about what kind of rocket launchers the Iraqis have.
Now the envelope starts to close: the pilots are approaching the end of their alloted time, and the vehicles are approaching a village. Rather than waiting for an ID, or getting more target information from the ANGLICO, or setting up a closer pass for identification, or even trying to ask permission to engage (assuming they needed it), they roll in, guns hot, after not-quite IDing the target from 6000 feet.
You can imagine the surprise of the ANGLICO, who the whole time was working on a different target, when all of a sudden his A-10s break off and engage friendlies.
The aircraft acted independently of the the terminal controller.