Not true. If you buy 5 firearms at one time, you fill out the Form 4473 and each firearm is listed on the back of the Form 4473. If you buy only one, then the FFL will draw a diagonal line across the remaining empty lines in the table. If I were to purchase 3 stripped AR lowers, I would fill out the Forn 4473 and each serialized lower would go on a separate line. My local FFL/transfer agent charges me $18 to transfer N number of items on one 4473 from a another FFL. I have to pay $18 for EACH different FFL, but only once for multiple items from the same FFL on one 4473.
OK, so instead of saying "a form for each gun", I should be saying "one form for multiple purchases, as long as the serial numbers for each firearm is entered".