I suppose that is where I think many are just not framing the issue correctly. It’s not a difference of rules, it’s a difference in controllable quality of officiating.
One set of teams that are playing in matches with VAR will (or at least *should*; we’ll assume VAR is not being used for manipulation for this argument) have an advantage over the other set of teams playing in matches without VAR, because their matches *should* have a much higher likelihood of being more accurately officiated, meaning they are less likely to be unfairly impacted by incorrect decisions by the officials. The results of matches using VAR *should* generally be more “fair” to the actual sporting actions on the pitch than the results of the matches not using “VAR”, which is a disadvantage to teams playing in the matches without VAR (as theoretically the quality of their performance contributes less to the match result than the quality of performances of the teams in matches with VAR). Simplifying it — likely too much, admittedly — matches with VAR *should* have less randomness than matches without VAR.
If the argument was put that VAR should be used for all matches or no matches in order to ensure no teams have an advantage of higher quality officiating (which, again, causes variance in the impact of the quality of performance on the match result), then they may have a decent point.
But then there is the utilitarian counter argument that can be made that it is better to improve the officiating for some teams rather than purposely allow the lower quality for all teams. But comparative utilitarians would then say that you are not actually maximising good with that setup, but rather creating a small class of teams receiving the benefit.
Ultimately, this is a question of fairness, but one of accurate interpretation and application of the rules, not of variation of the rules themselves. And it’s a difficult one to authoritatively answer.
