I think he's talking about that 5-6 seconds window that you see when you join the server.
It says "thank you for supporting our servers.." or something similar, and it countdowns to 0 seconds, and it has an "enter" button that you can only press after the 5-6 seconds.
During those seconds, if you join a team, you spawn but can't move until that window closes, so in worst case you might lose 5-6 seconds from your protection time.
Solution : don't join a team before the countdown finishes. Then you can press "enter", join a team, and instantly move.