We always get bogged down in this stupid argument. 60% is in fact 60%. The reason you think it’s not is a combination of confirmation bias and a completely crap mechanic.
The real problem is when you accomplish something it would be nice to get the reward you earned for the work you put into it. This RNG garbage is far too prevalent in Diablo 3. It doesn’t help the player to enjoy the game to fight your way to a new Grift tier and whiff your gem upgrade repeatedly. Because of the randomness it’s just as likely to walk away with zero upgrades as five. Stupid Design. If you mean the average to be three upgrades out of five just give three upgrades and be done with it.