The old Beech 200 Sim the RFDS use is a ball breaker if ya below par, a great tool to filter out those that have gotten there by 'other means':-)
Even the most sophisticated Level D full flight simulator is a "Ball Breaker" if the simulator instructor or check captain is the personality type that likes to humiliate a candidate. The King Air simulator is very old as you say. As many have testified it behaves nothing like the real aircraft. Especially on the ground.
If instrument flight hours were so important as to be considered a specific limitation for an RFDS interview, then don't you wonder why the more sophisticated operators such as Qantas, Virgin, Cathay Pacific, Jetstar etc do not include minimum instrument flight time experience for interview purposes? Whoever writes that RFDS advertisement is either naïve or has little experience in the real world of how many pilots easily fake their instrument flight time.