The obvious advantage is the experience it gives these guys working with their new teammates, Jeremy Kerley and Scotty McKnight with Sanchez and Greg McElroy with the receivers. Not knowing how long training camp might be, this could at least mitigate any loss due to the labor situation and get these guys comfortable with their surroundings.
Just as important might be the help these guys get in learning the playbook. The team has not even been able to give any rookies a copy of the playbook. The only exception might have been Muhammad Wilkerson, who was picked during that temporary respite from the lockout, but he is on the other side of the ball. These guys were able to get a look and learn some of the intricacies from guy who know it can can coach them that they might have missed due to the lack of a rookie camp.
None of this is a perfect substitute, but it is better than nothing.
Stuff like this is also why I thought the team was right to keep Brian Schottenheimer for another year. This lockout would be much more painful if the entire offense did not know the system than a few rookies.