I agree with your differentiation between RNG and probablity, but you can't compare randomness from games to randomness from players.
Difference is that human psychology is not random and player decisions are 100% made by the player himself and are thus completely controllable. Its a difference wether you get rekt by a lucky mortar shell or your opponent caught you off guard with an unexpected build-order.
I would even go as far as to say that exactly there lies the "meat" in a lot of competitive games, as you are truly playing against the other player, and not playing against the game per se.
Human psychology is not random, no. But technically nor is computer RNG: it's grabbing a value from the system clock. The important part is your opponent's plans and the results of the dice rolls are both hidden from you.
You don't know what your opponent will do: you know what can happen and if you know your opponent you can judge how likely each outcome is. But until you see what they did it's effectively chance. Probability.