Halo 4 xp cap loses your xp?

Okay, so I hit it today after a pretty extensive day of gaming. However I didn’t stop when I hit it due to having quite a lot of fun gaming with my friend. In the last game I played I hit a few commendations for a good few thousand points and it got me to thinking… if I hit something like that after the xp cap is it lost for good? because that just makes somethings a bit stupid… people keep waffling on about 600 microsoft points for nailing 140 hours of multiplayer in the first month of the game, yet if you do good, you lose points due to an xp cap? Seems a bit of a stupid call to me…