I know why CP Kestrel isn’t higher up.
I even asked Broken Myth themselves on twitter, and they gave quite a satisfactory response.
They said that CP Kestrel in the hands of a mechanical god is amazing but it is difficult to find that in soloq these days(that’s right it is a soloq tier list) so they put CP Kestrel as B in both Mid Lane and Jungle. Jungle it is more understandable due to the fact that Grumpjaw, Alpha, etc are pretty much dominating the jungle atm. But as Mid with the extra gold, CP Kestrel would be S-Tier if it was NOT talking about soloq as she can get her items very fast and snowball for a quick game.
CP Kestrel is amazing, and she is deserving of a higher place in the Tier List, BM admitted that, but because it is a soloq list they were forced to bring her down due to her high skill cap.
It is rare for me to see really good CP Kestrel in ranked these days and I am T6 silver in 5v5 atm…