Sorry, I should have made it more clear, the unwritten rule is the first production of a Tesla Model goes to who pays the car in full to Elon in person.
First Model S went to Steve Jurvetson because he wrote a blank check to Elon as soon as he found out about it.
First Gen 2 Roadster will go to Konstantin Othmer (Elon required him to go to Tesla HQ in person to pay $200k and sign agreement).
First Roadster/Model X went to Elon (I guess for X no one did that; first Roadster Elon wanted it personally), Elon only got Model S #2.
The unconventional way Elon Musk decides who gets to be first to buy a new Tesla
I imagine this case was no different, board member Ira Ehrenpreis most likely paid in full immediately.
As for the slot swapping, I imagine Elon just gave his own slot back to Ira. It is highly likely Elon had his own slot (perhaps #2). Perhaps that is allowed anyways without having to go the gift route (a mutual slot swapping doesn't really affect anyone else).