I’m not sure KG was upset by anything. KG was in the first 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:

youtu.be/hVtPyNHq_Jk?si=1ds3cHq4HwXGWi6-