Referees have one standard, the standard they use to determine if an action is a penalty or not. It is important for the referee to constantly refine and re-enforce that standard in their reffing as often as possible. As such, it's clear that they should use the same standard during practices as they do during bouts, to grade things using the same standard or threshold all the time. Ideally coaches will understand and agree with this standard, but that does not mean that it is the standard that they will use.
It is in the coach's best interest that their skaters never get penalties, are never even in danger of getting penalties. So, for instance, a forearm to the back that has no effect on the other skater will not meet the standard of the referees, they will not call anything. However, the standard held by the coach of what is an objectionable action may well have just been met, because this action puts their skater in a position to possibly draw a penalty, depending on the offended skater's reaction and depending on how strict the given referee is calling the game or how they see the action (all things out of the coach's control). So the coach will look to control what they can, and what they can control is their skaters, and they will want them to avoid being in that vulnerable position by never putting their forearm on a player's back at all, to avoid the possibility of a penalty by avoiding the action altogether.
It should be clear then that there are these different standards, it should be clear how they sync up, and the ways in which they can be out of sync. The point of this discussion then is not that every disagreement between coaches and referees, at practices or at bouts, is going to be the result of differing thresholds. It is not to insulate the referees from criticism in these situations, for to insulate referees from criticism is to protect them from improving, something we cannot do. I discuss this though because I have seen referees in many situations, where in drills or scrimmages, convince themselves that they must be missing calls because the coaches continue to yell at their skaters about their forearms or hands, and it is this concern that referees must insulate themselves from through a better understanding of these different thresholds.