In CDG 2E this is common business for at least several months now. I assume it is all AF anyway so they know what to check for ? It is indeed happening in the queue just prior to passport control. They will pick out individuals passing through that queue and guide them in a small separate lined off space where they can measure and weigh carry on. If all ok you get back into the queue. If there is a long and slow queue then this is actually a shortcut ;-).
Nothing of this in the SkyPriority lane though - checks only happen in the normal queue.