As CE mentioned above, there are no rules. Most of the big time programs will over-offer and be "relatively honest" with kids, telling them they're a Plan A or Plan B kid. (Plan B meaning they might have 4 scholarships available at a given position and the kid in question is #5 - #8 on their wish list.) This is not as bad as it sounds as most kids will learn their true market value throughout the process. (I.E.: They get 10 offers from various programs, 5 from power five programs who either slow play them or openly tell them they are a plan B kid and 5 offers from mid-major programs who make them a priority).
Where it gets kind of ugly is when a coach has a kid on his Plan B list, accepts the commitment, then gets a commitment from one of their Plan A kids, then goes back and tells the Plan B kid that they want to withdraw the commitment and tells them to look elsewhere late in the process when many other teams have filled their commitment spots.
Again, there are no rules.