Oddly enough, Nigerian pilots and techs were roaming around the halls of PAC well before any inkling of a deal was in the air - so the “evaluation” was underway which then slowly started leaking out. However, the Nigerian deal was announced after their first JF-17 was already on the line and that is fine if the buyer requests it that way.
You can actually have training and progress without the announcement. I attended a strategy event for a client with whom I’m closing a fairly large deal - and even though it’s still sitting with procurement and legal they consider it done.
Now, can someone throw a wrench in there?
Very likely, this is what happened to a deal with HCL I nearly closed until some wanker said they could do it in house (and they couldn’t) but that is normal.
The same goes for done deals too - Take the Pakistani AH-1Zs - 12 ready for delivery and less than a month left to ferry them all falls apart because of Trump. Now they’re being pushed to Slovakia and even Ukraine wants them.