See, the door thing isn't such a big deal. Nintendo must already have TWO door opening sequences, because you can open each door from both sides... so there's two animations, one where Link opens the door on the left hand side, and the other with Link opening the door on the right hand side. There's two options: either change the code so the door opens the other way around, or change every single door so it's "backwards" as to how it was before.
The way I thought about it is that it changes actual play dynamics: because Link's traditionally left-handed, players naturally place themselves so that their right side is covered and their left side out in the open, when trying to attack, so their sword won't hit the wall, and vice versa when defending. There's something similar that applies to the use of the bow and arrow, etc. but for the life of me, I can't remember how that works.
To keep the play dynamics the same, the whole world is flipped, so players use the environment in the same way. It's possible that some parts of the game are designed with giving players the right amount of cover in mind... a right-handed Link in a world designed for a left-handed one would be left out in the open with no way of defending themselves.