What is the purpose of the revolving doors before immigration in CDG airport?

When exiting a flight originating from outside of the EU in CDG airport recently, I noted a long queue forming behind a large revolving door, between the exit of the aircraft and the immigration desks. The revolving door did not move in a constant way and had signage indicating for 8 people to enter and then exit, before pausing to allow 8 more passengers through. There was actually a much longer queue behind this door than there was at immigration; the immigration queue was only one minute long. Interestingly, the door also had one 'stop' inside the airside terminal waiting area, and one at an adjacent plane entrance.

This door was the only thing between the airplane exit and the immigration queue. My guess is that such doors are designed to restrict passenger flow, but this seems a bit pointless given that people are queuing for immigration immediately after it anyway, and normally gather in large numbers there.

What is the point of the mystery-door? Did they install a passenger flow restriction door so that the airport employees directing passengers into different immigration queues have an easier job? If so, why is there an inlet coming from airside?

It's a stupid question but I couldn't help but wonder during my long wait to pass through this door.