Rear derailleur doesn't go to smallest cog
The inside of the barrel adjuster should screw into- and out of the derailleur  when you turn it. The part around it should only slide lengthwise but should turn with it (there is a slot which allows it to slide lengthwise but ensures they turn with each other).
In my experience the Ultegra R8000 barrel adjuster has an unusually fine thread and needs quite a few turns to move a real distance.
If your second rear wheel is really identical to the first one (same hub, same cassette, same spacers on the cassette (if any) etc.) then it shouldn’t require derailleur adjustments. But I guess different torque on the cassette lockring or some other minor difference could be a reason.