Sub has an easy game plan so you can spend your brain power trying to optimize usage of wakeups, flawless block, and the other components of the game. In a month, sub will be considered average just like skarlet will... People will figure out that if they ever guess the high correct, Subbie is free, which means while there are mind games to let the 50/50 work, blocking low vs sub as default is freelo. Because of the lack of damage in SZs kit, they only need to guess right a third of the time to even out the damage and if they just guess right more, you lose.
SZ will be a flash in the pan and Reo's S tier rating will disappear. I think he is fine as is but the overhype is ridic.