The problem isn’t in the simulation part, but in the “supports” part.
You can certainly write a simulation in which an agent decides to take both boxes. By the conditions of the scenario, they get $1000. Does this simulation “support” taking both boxes? No, unless you’re only comparing with alternative actions of not taking a box at all, or burning box B and taking the ashes, or other things that are worse than getting $1000.
However, the scenario states that the agent could take 1 box, and it is a logical consequence of the scenario setup that that in the situations where they do, they get $1000000. That’s better than getting $1000 under the assumptions of the scenario, and so a simulation that actually follows the rules of the scenario cannot support taking two boxes.
This view appears to directly contradict the lines “Better for you if you take me off” in conjunction with “The earring is always right”.