The transaction as described above is not a drop shipment though.
From your link:
The FFL didn't buy the gun.
Again, I'm not arguing, merely repeating was has been explained to me - by folks that do this for a living.
The transaction in question has been explained as the "three party" sale as mentioned in the bulletin early in the bulletin.
Drop shipments involve the sale of goods by a seller who delivers the goods directly to the purchaser’s customer. However, this is generally not a three-party transaction, but two two-party transactions.
This is also the one that may cause problems for the "group buy" folks.