Wether or not the rule is stupid, the simple fact is that both fighters agreed to the ruleset before the fight, therefore if Jon Jones used an illegal move he is at an unfair advantage since they are fighting to different rulesets. This precedent is insane.

Imagine you agree to run someone for 110 meters. You perform the race and you narrowly win. Then 10 years later the guy who lost the race says that its stupid to run to 110 meters and not 100, and he was ahead at the 100 meter mark, therefore he is the winner.

Would anyone let something like that happen in any other sport?