There is no way that this is possible. Niemann's performance has such a wide variance between: - his best days, where he is pressing for victory or easily winning against the very best players in the world (not only Carlsen, but also Aronian, Mamedyarov, Firouzja), and - his bad days, where he plays like an average grandmaster.

Someone who can play as bad as Niemann does on his bad days could never beat Carlsen legitimately in my opinion.