Even if they provided a percentage other than 50%+ there would be no way to prove it. The rng is stochastic, meaning the random instance resets after each roll. There's a 50/50 chance you'll get heads when you flip a coin, but if you get tails, the instance resets and you're no more likely to get heads. If you get tails ten times in a row, it's unlikely, but it doesn't prove it's a trick coin. It's just bad luck. Even as unlikely as it is, you could get tails 100 times in a row. It's unlikely but POSSIBLE. This is the nature of probability in a stochastic instance, and this is why the rng in Destiny has always been so frustrating. They can fiddle with odds for in-game and paid loot box rng and it would be impossible to make any assessment without disecting the game's code. This is why when they introduced a weapon called "The Stochastic Variable" I almost shit out of my mouth. That was a very hard troll on their part.