Many game that depend on RNG remove the "randomness" from it. For example in DotA games (LoL or DotA 2) if you have a spell that has a 50% chance to stun someone, it's not exactly 50%.
For example, Slardar's Bash has a 25% probability to Stun the target. On the first attack, however, it will only have an ~8.5% probability to bash; this is its PRD constant C. Each subsequent attack without a bash increases this probability by 8.5%. So on the second attack, the chance is 17%, on the third it is 25.5%, etc. After a bash procs, the probability resets to 8.5% for the next attack. These probabilities average out so that, over a moderate period of time, Bash will proc very nearly 25% of the time.
That is entirely due to how they decided to implement their system and nothing to do with "RNG".
I assume the real reason it's setup that way is because players in a competitive game don't want "luck" involved or at the very least want it's effects to be minimized as much as possible, such as the system you quoted.