I’m not sure where but I know it was a point of contention that they made up over. There was a moment where tenacious D was brought onto stage as Jack Black and that pissed/hurt him a lot. So what they are saying is kinda of true but they’ve already talked and made up so why they are bringing it up as a gotcha is a bit strange.
I'm not sure KG was upset by anything. KG was in the tenacious d movie and I feel like if he liked doing movies it would be easy for him to do bit parts in movies with JB. Also they made fun of this in a song they did so it can't be too serious of an issue: