According to Z90 manual (p. 156), Face detect auto focus is supported when recording XAVC QFHD. But in the menus, "face detect" greyed out. If I switch to XAVC HD, "face detect" is selectable. I'm pretty sure no other setting is interfering. Do you think I am doing something wrong, or is there an error in the manual? Thanks.

Never mind. Figured it out. There was a setting interfering. Video out for QFHD was set to SDI. When I set it to VF/LCD, face detect is now selectable. Makes sense since the LCD is used to change priority face.