they are for heat sinks so when you open the door then close it it will recover temp faster
The bricks effect on recovery depends on your definition of recovery.
When you open the lid and release the hot air, the recovery time is how long it takes to replace that heat after the lid is closed again.
The firebox design, draft efficiency, cooker volume and amount of hot gas produced by the firebox are much bigger contributors to recovery time.
In fact if the lid is open long enough for the bricks to cool a bit (they begin to cool immediately), it will slow the recovery as the bricks consume some of the heat energy needed to come back up to temp.
The added mass will change the recovery
profile, so the temp will rise faster initially as the brick gives up heat to the air (This is what many refer to as "recovery").
However the rate of recovery will slow as the air and brick both need to increase in temp again.
To reach the same initial stabile temp will take the same amount of time with our without the added mass.
You'll just get closer sooner with the added mass.
Do you still need them if your using a baffle or tuning plate?
You really don't need them at all.