Last time I connected via YUL to US (July 2023)...
1) There was no priority security. AC staff were pulling people to the front of the security line based on upcoming departing flights.
2) The GE border line was a bit of a joke. Sure, it was not very long (maybe 5-6 people?), but ADM staff kept alternating between the GE line and 1-2 other regular lines to flow people to the supposedly GE-dedicated border control counters. Probably as a result of that the US CPB folks appeared to treat everybody the same, regardless of whether they previously interacted with the GE kiosk or not. A first time in a while for me where I actually had to show my passport at pre-clearance.
This really made me reconsider connecting through YUL on the way to US.