You see this:
That is a reasonably highly upvoted post regarding issues with the visibility of Sand Ekko's effects and a glitch giving away his position in the jungle which another poster also experienced and whose reply noting that is also upvoted fairly strongly (for Reddit). These indicate the issue brought up by these posts is fairly common and observable in-game regardless of game mode.
An issue that makes a champion that is entirely balanced around reading his effects harder to read if he buys a skin and causes the champ to occasionally be spotted without there being any wards spotting him.
You know what could keep this kind of thing from affecting the fairness of Ranked games (which have setbacks incurred if your lose)? The thing I suggested that is proven to work fine that you refuted with what amounts to "I'm better than everyone else and the bulk of the player base doesn't matter."
But of course apparently this information is totally useless and should be ignored according to you because the poster of the remark gleaned this issue from playing against Ekko in non-ranked play and and otherwise identical game cannot provide useful information because people who don't play for post game points that do nothing are inferior to the Ranked game master race. And you are totally right. There should be no grace period shielding people from possible missed bugs/imbalance/newchampspammers because if they can't play well enough to counter it they don't deserve the LP. So long as you don't have to play normals to play the new champ for a week.