For some reason I haven't tested undoing the moles, so maybe that's the reason. Sorry about that!
The thing about redoing tiles overall is that you're able to cheese some levels, you don't really need to think about the path you're going to take, since you can just fix it by redoing the tile. I played it for a bit longer and realized that it does not apply to tiles at the border, but other ones as well.
On one hand I understand the intentions behind that (thats why I'm uncertain as to call it exploit ), it gives a less harsh penalty on the player. On the other, it may trivialize some puzzles found on the game. Maybe I'm sorely mistaken, but the redo button works less as a way of putting the player back on track and more to get away with mistakes.