I just checked this, and it is weird that even on the fast speed, you can still "speed up" like in the other version, but the speed stays the same and only your position changes. I understand they did that to help avoid enemy fire, but I think that is what makes it not obvious that you base speed is different. Excellent job figuring it out though. Add it in with Breakout to Atari published games that get the difficulty switch positions wrong in their manuals.