I think it's just the fact Afrifa has shown more the last few months alone than Kerr has during his entire MLS tenure so far, his play, the goals he's scored, how he's set up his teammates, it's pretty clear as day who has been better this season. Kerr can get there but he needs to consistently start scoring or setting up others to score. I think it also helps that Afrifa is more of a winger, and with Tajon out, he will be much needed for the upcoming windows until the end of the year.
He broke out only in the last few months and looks to have solidified a starting role for KC now.