Ah, learned something new today. What is benefit of unremovable bearings? And could OPs gap have something to do with wisaligned O-ring? 2mm seems a bit much to be normal.
The "benefit" is to CK, I guess. You have to send the headset back to them for repairs or replacement. Maybe it assures the bearings are installed and aligned properly. The bearings can have the seal popped out and regreased in-situ if you want to bother. Fortunately they have a 10-year warranty and I haven't had any problems with mine in 5 years so far.
The O-ring is a tight fit on the steerer tube and can be knocked out of it's retaining groove in the top cap if you don't install it carefully. King's installation instruction sheet particularly warns against this. I filed a slight bevel to the outside top edge of the steerer tube and put a little silicone grease on the O-ring to make the top cap installation easier.