Very often the way with wheel bearings. It took ages to figure out which one it was on the TT since all the wheels are so much closer to your head
It was only when it got bad enough to make a distinctly different sound when turning right vs left that I worked out where to look.
The original factory bolt for the 20" cars is a 19mm hex, but it is dimensionally identical to the standard bolt for everything else and takes the same torque so the aftermarket ignore it and supply the 17mm. No idea why Audi made a special bolt just for the 20" when its the same CV joint, same thread, same length, and same size head.