Not sure how well known this is, but the select button acts as an auto-key in the game, besides it's use to bring up the map. I can't remember off-hand if it's auto accept or cancel. However, I just discovered that when walking around, holding a direction and then holding the select button will make you move at TAS speeds. I'm not sure if it's frame perfect movement, but I doubt someone could do better manually.

I think it's intended behavior for the game as well. Like you said, it's in every version, and the only place it doesn't work is the overworld map, I think, for obvious reasons. I'm really interested in watching this, GG and congrats!