Again.....
1) Hand signals
2) Down & Distance
3) Personnel groupings
Now, what's not on that "advanced scout" film is the All-22 which they can easily put together with the 3 items above.
Now Billy B knows what plays are called with those personnel groupings matching the play with the hand signals.
I don't think it can be much clearer. It's cheating & against the rules. Plain & Simple.