Maybe I am confused on what you're clearing, but couldn't you just go into the retail dashboard (I assume you're using an XDK or hacked console) and clear the HDD cache that way vs having to play another game in order to clear?
It helps reduce load times for people who are playing the same game day in and day out. Same thing happens on the original Xbox.
I do so little with the 360 stuff, and most of it is older anyway, so the updates just make little difference.