trail vessel
As the game goes on squads slowly lose players, making what were full squads 4-5 man locked public squads. If it were a party that got put into the same squad I'd understand, but when it's the entire lobby being put into locked squads it makes it difficult to join another full squad if you wanted to leave for whatever reason.
If this was done to make squad swapping for buddy spawns harder I can somewhat understand, but a better alternative would be to have a 3-5 minute timer that disables you from joining another squad when you join a squad. This timer would not come into effect until the match starts and players can run freely.
I don't think it's a big deal, but I don't see any reason for the squads to be locked initially, most of the squad leaders have no idea they're probably squad leaders or even care about the size of the squad.