As I said, I can only assume. An autoland function is a precision function (well I don‘t need to tell you something that you know much better than I :D) that in a sim should follow real limitations and quirks. I think that it‘s much more difficult in a real aircraft to make it safely follow the ILS impulses dealing with a real atmosphere, thermals, etc while operating within CAT requirements than in a sim to read a bgl file and fly down a 3deg glideslope to the runway and showing a light or FMA here and there. A relatively simple Aerosoft Airbus can do it as well as a highly simulated PMDG 747. The question is probably more the correct simulation of the actual aircraft than to hit the landing zone. But I guess the AI pilot has a „harder life“ as it has to fly a whole circuit procedure and land any aircraft, regardless of whether it has an autopilot at all. Every change to the background sim would require new adjustments.