That makes no sense.
Because an ill-informed shift manager got his ... handed to him for making up a stupid rule you think corporate is going to through up their hands and say "Ok, ok now nobody gets to use CCs on GCs"? I think not.

The MOD was obviously over his/her head on this one.

But in their defense I would rather deny a sale and have 1 pissed off customer than authorize 5k in fraudulent GC purchases. That'll comeback on them. Retail employees are always on the lookout for potential fraud. And fraudsters are thinking up new and innovative scams everyday. They'd be long gone before you know you'd been taken. So some out of towner strolling into a seldomly shopped OM looking to buy ALL of their highest denomination GCs in one swoop is going to set off the ol' spidey senses.

With virgin stores and staff I always advocate extreme moderation (1-2) to see if they are hip to the game. If everything goes smoothly (either they already know what to do or you have to walk them through it) you can ask if you can get a few more OR simply comeback a little later.

You aren't likely to stroll into a new town drink their booze, oogle their women and buy up all their GCs without some resistance.