Pulling into someone’s driveway isn’t trespassing as a general rule, unless you know they don’t want you there.
Trespass at its heart is legally something you need to have had intent to do. “No trespassing” signs or verbal warnings to leave inform someone that this is land they aren’t wanted on, so are pretty important in proving trespassing.
This is also why door-to-door salesman and missionaries aren’t sued out of existence. Both use the land in an attempt to offer something to the owner, its a legitimate use, as long as they leave when told.
But since the delivery man believed he had explicit permission, since he thought this was the house that ordered a pizza, it’s perfectly legal. He just would’ve had to leave when he was told to go.
But the pizza man did nothing to provoke shooting, so I expect the owner gets no self-defense argument here. Just the pizza guy.