
Perhaps there is a distinction between games vs story /simulated reality, stories there is a limit, narratively it is important to have the idea of absolutes, Eventually, there's a point that something is so powerful that is meaningless to make any distinction between what is S - Rank and SS rank.
In games... I think it is purer to data crunching for stats, ones and zeroes, that you can define something as a reachable S class but when players beyond that in effect making SSS or S+ tiers.
And then that existed in games it pushes for stories to have tiers above...
There are stories that use a material ranking system too.