[Ordnael92]

He could still claim you gave him those instructions, and face some harassment from him in case thing go bad, I wouldn't risk it

Isn't the outcome the same as when you fake sign and then claim DNA?

Not really. Pushing the 2 situations to the extreme:
1) you signed with a fake name. The delivery man comes back to your house, but you're under no obligation to answer him. Unless there are cameras all around, there's no proof it was you receiving the parcel and signing for it. It's your word against the delivery man's.
2) you told the delivery man to drop the parcel to a safe spot during a phone call. He may well have been recording that call or, at the very least, have proof of having called with you answering the phone. That could well be used against you.