% Chance to increase potential tier?

For years there has always been one group wondering if there is something wrong with Nexon's use of RNG after they say failed 10 mastery books in a row, or failed 3 90% potential scrolls or like in this case have continuous bad luck with cubes, and another group always eager to jump in and say 'naw you just had bad luck', as if Nexon couldn't possibly screw something up.
Unless someone rich someday does some huge number of tests to prove one way or the other with 99% certainty, neither side will ever convince the other.