Yes, and people seem wise to this trick now and it’s totally open to abuse. Before a recent flight from T5 I watched around 20 people check their carry on bags in exchange for priority boarding (including small items that really didn’t need to go in the hold). On the jetty as I passed by was a single lonely bag, the others were all taken onboard. Oh, and the pre-boarding baggage cheats went before group 1 again, despite the announcement saying they would board with group 3.