Exactly, there are many ADIRU systems, and not all have a GPS update. The Boeing variants that are certified down to 0.1RNP would have to have this, or the drift rates would push it to a 0.3 RNP...
Honeywell recently announced their ADIRU for the Airbus 300 family, so it will take a bit for the certification to catch up. The A380 is already certified.