I understand that this hints avoids creating a user. But is there any harm in creating a UID 500 user? In other words, if resetting the welcome bit is sufficient to get the Welcome Assistant (which I do not know), how hard is it for the next owner to delete a user?

If the computer is received by a seasoned Mac user, creating a new account and deleting the old is no problem. If it goes to a new user, they have no idea how or why to do this.

I've had many clients in the past where the only account on the machine was "Mac User" or such and the password of "password" or none at all. It's the way they got the machine and the didn't know how to change it.

This process eliminates that situation. There's no account at all until the new user creates it.