Makes sense to me. I keep all my games on a 7200rpm drive with 8mb cache.
Games don't just load things at the beginning of a map... they often load new objects and enemies in the middle of the game, so the faster the drive, the faster these will load, and the less likely that they will affect the frames per second.
Soldier Of Fortune II is a good example of how a game loading objects can affect gameplay... I could always tell when an enemy was coming, cause the game would slow down as it loaded the new objects.
-Ryan