I read in a book, I think it was "The Water Boy" that coaches will move a player to the second team at times so that player can focus on a certain aspect of his game, and the assistant or specialty coaches can focus on that area (like footwork or what ever.) and work with him more exclusively, while the Coordinator works with the first unit as a whole.
Kind of like pulling a player aside, putting him on the second team and saying, forget about the scheme as a whole for a moment and let's just work on this for a while?
Perhaps this is what is going on.... Especially for Rookies in OTA
""People Will Probably Never Remember What You Said, And May Never Remember What You Did. However, People Will Always Remember How You Made Them Feel."