The passengers disembark.  There isn't, actually, any nonsense about leaving carryons behind.  Somebody might have something important in there, and nobody wants to make a show of discipline by forcing them to abandon it.  It's simpler to disembark by their usual deboarding algorithm, which is actually quite fast if you never have any crowded aisle, and most passengers have disembarked through clear aisles walking forwards in unison before anybody with an even slightly complicated deboarding procedure tries to deboard.

The passengers disembark.  There isn't any attempted nonsense about leaving carryons behind.  Somebody might have something important in there, and nobody wants to make a show of discipline by forcing them to abandon it.