I'm slowly working up to that level, so let me take a stab at it. ;) What we've done for years at the 4th grade level is take a count of players during warm-ups to compare to what's written the book, strictly for "preventative officiating". In other words, if the number of players on the floor agrees with the book, or is less than what's in the book, we're good, and there's nothing more to do. If the number on the floor is greater than what's in the book, we try to find out why. Did a player not get listed in the book? Is someone on the freshman (oops...3rd grade) team warming up, and they will never get in the game? We ask the coach and scorekeeper, get an answer, fix anything that needs to be fixed, and away we go.

I know some officials who take the book to each coach to have them verify all the names and numbers prior to the 10-minute mark. I always ask them why, and they tell me the same thing - it is preventative officiating, and if there are any book issues later, it would be easy to see it's 100% the coach's fault. I believe the IHSA also recently started requiring officals to do that in post-season games.

There's obviously no requirement otherwise to do it, but I think the reason a lot do it is because they want to avoid issuing penalties for "technicalities", rather than issues involving the game itself.

Keep an eye out for more players coming from the locker room. Other than that, since there is no penalty to be avoided through preventative officiating, there's no need to take any action.

The goal is to keep the game from being decided by a scorekeeper's error. Since points aren't going to be scored from too many names in the book, there's no need to worry about it.

Agree.

I would also add, that it may also jog the coaches memory. When I have more players in the book than I do on the floor I ask the coach is they are aware of that and if anyone else is coming. Usually, a player is sick or suspended or whatever and the scorebook keeper just copies one game to the next. THey also may have replaced a 'missing' player with someone else that may or may not be in the book. Or the coach may be expecting more people to come out of the training room/locker room then are in the book.
To me it is good preventative officiating, even though there is no rule!