1. The discussion setup where you imagine a counterfactual is given by magic does not entail that magic can do any other thing you choose.
“Imagine I give you $100, what do you spend it on?”
“A McClaren, since you could have given me $300K”
2. Taking your question directly: because these are not closely related problems.
My question was a sincere ask to define, in this scenario, what is prohibiting that other magic?