I think there is a certain timing to movement - if you press a key too soon after the last move it will register in the game a little later rather than immediately and this makes it easy to press too many times as it feels like the key did not work the first time. Once you get used to it I think it can actually help you move around timed puzzles quickly, as it works a little like queuing one instruction giving you more time to think of the next move.

Dungeon Master had the same feel to it, so I guess the devs made it like this deliberately.