“Why are there no official Statistics regarding champion WR in different Elos?”
Lol? What would that prove?
If a champion is innately “stronger” than others, a player preferring to use them is going to be put in an elo where they have a roughly 50% winrate. That’s part of why winrates are a poor measure of champion “strength.”
The only way you’d get a decent measure of champion “strength” by using winrate elos is if players picked their champions at random. But most don’t. Most have a few preferred champions which they practice and excel at, and that determines the majority of their games and consequently the elo they’re placed in.
Winrate is not = champion “strength”
Edit: so, to answer your question more precisely, I would guess by saying they haven’t published that info because it is meaningless data. The utility of statistics needs to begin with a question and a following hypothesis, and then gathering data which will point to either proving or disproving a hypothesis.
But starting with data before positing a question can trap individuals into drawing erroneous conclusions based on their preexisting notions, which can be very misleading.