Okay, these are just my thoughts and I may not be 100% accurate as this is based off my own personal experiences, BUT I think it's because lack of feedback on the PBE as more people are inclined to test out new champions instead of skins. I was still maining her at the time when I got my access and only play on it every few weeks or so.
However, that being said, I can usually get a game with her and her new skin as everyone else was fighting over Camille. I went on there when she was released because the first couple of days, I say good luck because everyone instalocks things in blind pick. I gave feedback on Arcade Ahri, the Lux W changes and a few other things, but it seems that people treat that place more like norms instead of a grounds for testing bugs.
Okay, I get we're supposed to play actual matches, but whenever I find a bug, I can never get the enemy team/my team to cooperate to see if it's just me or it's a global thing. With a skin as complicated as Elementalist, it'd be extremely difficult to get enough feedback from the ~1000 people who play on there, about 1% who are going to go into a match with that skin.