Searing question about pellet grills

[actech]

I am a new pellet grill owner. (pit boss 820) I have seen where others have searing plates, the pit boss has a slider that opens slots to the fire pot. Is that the only location to sear?  I'm not understanding how a grill that is at 500* doesnt sear when the meat hits the grates???  My rusted out rotten charbroil has cast grates that will fit the pit boss. (only thing not rusted and rotten) would it be advantageous to try those in it?

thanx Kurt