I think the OP is referring to a Play Now or online ranked game against his co-worker, where as I guess you are referring more to team playbooks in Franchise Mode. So there really wouldn't be teams becoming familiar with playbooks, they would have to use their default playbook, just like with the rosters or suffer a applicable ratings penalty on plays foreign to that book.
Also, I don't agree with the bold part seeing as people switch playbooks in Madden so they can find plays that don't exist in their teams default playbook, so adding an applicable ratings penalty to those foreign plays, makes perfect sense, imo.