Water Heater (Suburban SW6DE)

Going through the systems on the new to us 2006 3023. As I expected the anode rod is pretty well used. The structure is about 85% there but it has lots of small holes and is caked with calcium deposits. That part of the fix is pretty straight forward.
Today I looked a little closer while the gas burner was on and noticed large chuncks, and small of metal laying on the bottom of the burner chamber.
There is a steel plate that runs the length of the burner chamber and the gas flame burns under it.
I got the manual out and it does not appear that the metal plate is rmovable or replaceable. I think there are two rivits midway on the right side as you are looking at the burner chamber.
Does ayone have experience with this situation? What is the cause and effect?