Sprockets have to wear in order to continue matching the morphing chain pitch.
With new chain and sprockets, the centres of the rollers will align with the pitch circle of the sprocket.
As the components wear, chain wear more so normally assumed, the sprocket pitch and chain pitch no longer coincide along the original pitch circle plot line.
To compensate, the drive run of the chain finds a position higher up on the driving teeth of both sprockets so that the respective pitch circles coincide.
So, IF the chain doesn't wear, it won't be forced to walk out on the sprocket teeth to find a pitch circle match.
This will improve sprocket life, note the word "improve" is not quantified.
Chain rollers of a non wear material will result in the mating material sacrificing unless it too is a true non wear material.
The presence of a proper lube will assist the wear resistance of the lesser material, namely the sprockets.
I found some of the BMW statements to be very carefully crafted.
I did not see express wording that no external lubrication is required, just an implied message of benefit due to no egress of the sealed inner lube.
Surely better sprockets will be available to better match the materials of the chain roller coating.
Better in terms of accuracy and running surface treatments.