I don’t think so because you can’t move your z axis in 2d. It doesn’t exist. So you need to be aligned with the correct z axis in 3d view. Fez is not a 2d + 3d platformer/puzzle game, it is a 2.5d game which is a mix of 2d and 3d art, not a mix of the mechanics. But I see where you are coming from. If changing to 2d and back changes the z axis, it defeats the purpose of puzzles since it would be really easy.
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I think that you would have different puzzles rather than easier puzzles, the challenges would have to come from the interaction of the different world views and the limitations that are oppossed upon you by them rather than the difficuly that comes from dropping down when switching views which imo is more of a frustrating kind of challenge than mental exercise.