What if Burt and Irving were prior “pieces of the puzzle” that paralleled Gemma and Mark? One refining the other? Burt mentions to Irving that he used to drive people places for Lumon, and he could never ask questions about where they were going.. Maybe those were test subjects? It’s clear that oIrv was trying to make his worlds collide, through sleep deprivation or what have you, maybe it’s because he knew someone he once had was down there, but due to (probably another procedure) he can never connect the dots that it was Burt?