S-ranks and VGU's

So, I know that S's are earned based on CS, KDA, objective control, etc... But as far as I was able to see this is all based on how many people play that champion in a specific role (kind of like an average over your ELO or something of that nature, which is why getting S's on popular/easy champions is "difficult" in their regular roles). So my question is when a champion gets reworked does it become "easier" to get an S-/S/S+? Or does that not really change too too much at all? (This is all going off personal observations btw I haven't been able to find any post/article/etc on how exactly to get an S)