both for letting players know what to expect like you said and for keeping fans from getting upset or going down conspiracy rabbit holes on why calls were/were not made. Broadcast the actual discussion and/or detailed reasoning from VAR officials and fans will be happier (or the way VAR decisions are made will quickly change if they don't make sense in terms of following the rules consistently). And that reasoning needs to be detailed, explain what rule was involved and exactly why the rule was or was not broken. No generalized statements. Player did X which breaks rule Y or does not break that rule for reason Z.

Also when incorrect decisions are made when VAR is involved the league needs to punish those involved in a way that will improve future decisions (incorrect as in the broadcast discussion from VAR goes against the actual rules for the discussed play). Whether that is suspending refs, sending them down a level for a while, etc. If the ref knows there is a consequence for not applying rules consistently, they will do so in the future. As long as VAR exists giving refs tons of time and information/angles to make a decision, full transparency in those decisions is necessary or fans will always assume the worst.

I don't watch those sports, but I feel like I hear about other sports like rugby where the ref has to give a full explanation for decisions to the crowd and there is not the same issue there with fans questioning calls.