At QF anything below Cat ll has to manually flown using the HGS. Since you have to disconnect the 2 axis autopilot right after touchdown to prevent unwanted roll input in lieu of yaw I think they settled on Cat ll being the limit for autoland. That also may have been informed by too many dodgy roll outs in other than low visibility conditions when the ILS wasn’t protected. A Boeing tech bulletin refers.
QF has of course only one HGS, and the F/O is subjected to 90 seconds of terror watching me be a meat servo while staring into the sole low viz guidance source.