After attacking Kagha and fighting the druids, Wyll teleported to the druid grove's gate and, while he still follows me and appears to be part of my party, he is acting like I never recruited him. He laments about the druids attacking, and then I have the choice of asking him to join my party or telling him to wait at camp. The former option causes him to enter the dialogue where he asks me to promise to help the tieflings, like when you first talk to him. The latter option has him say he'll wait for me at camp, but he doesn't actually leave.
I've tried reloading an older save and doing the fight again but got the same bug.
Screenshot below