Unrelated to this specific episode, but I heard someone say Burts innie is the one we saw in the season 1 finale. I think the elevator Irving paints lets innies leave work without getting deactivated. I think that’s why Burt has followed Irving around after.
“Think of it as a transition” - Milchick, speaking of Burts retirement.
Having Innies take over gives Lumon absolute control over them, since they can be “turned off” at any point