If you are really worried about that, how could hubs work a couple of years ago when the axle standards have been much more narrow ?
Your bearings will anyway die at some point. Also because the mounted bearings in new Chinese hubs are often not the best.
There are in fact a bunch of 21H 2:1 hubs/ wheels on the market, when you do a online research. Maybe that reduces your concerns. My first set of wheels ran approximately 500km before winter break.. that's not a lot, I know.. but that's the only reference I have so far. The second set is waiting for better wheather also..i built the wheels during Christmas time.
