I always take that claim with a pinch of salt regardless of who makes it. Just because the seller didn't fire it, that doesn't mean a QA technician in the factory, distributor, retailer, prospective customer in the shop, etc, didn't fire it to make sure the gun worked, do a test fire to see if they liked it or to see it was within legal limits for example. I assume it had been fired a few times before at some point between being manufactured and landing in the hands of the seller.
At least 3 of my guns have test fire cards/sheets in the box so I know the "never fired" claim is untrue anyway.