I am the owner of a bike with a DT Swiss RWS thru-bolt (kinda like a thru-axle but it fits in regular 9/10mm dropouts) skewer system. I saw in their marketing fluff that one of the supposed advantages was that you could put way more tension into the axle than you could using a QR skewer. Leaving aside any discussion of whether it's an advantage at all (indeed some users report that it's actually quite easy to strip the alloy threads on the skewer if you overtorque it). I was curious how this would affect hub bearing preload.
With most of the other wheelsets I own, skewer tension directly contributes to bearing preload and anyone familiar with the correct way to adjust classic cup-and-cone bearings will know that it's important to check the bearing clearance with the skewer/axle bolt tightened, if not it's easy to put too much preload onto the bearings.
Looking on the DT Swiss website, their approach to preload seems to be different. The inner bearing race fits flush to shoulders on the axle on both ends of the axles and the shoulders on the hub shell for the outer race are spaced slightly narrower. This means that the outer race of one bearing sits flush against the shoulder on the hub shell but the other outer race floats slightly off the shoulder on the other side of the hub shell and is kept in place with an interference fit within the hub. Through some physics that I can't quite picture, this means that before the wheel is put into the frame the inner axle exerts outwards force on the inner races, preloading the bearings. When you put the wheel in the frame and tighten the skewer, the inner races (and axle) get compressed, the preload is reduced to the correct amount (that is apparently independent of the skewer tension) and you're good to go.
I guess my question is why do they do it like this and is it actually any better for ensuring correct bearing preload vs. traditional systems?