You are correct, there is nothing holding the axle in the center section, that wheel movement you see is the axle pivoting at the wheel bearing, the end float in that clip is set at 0.004" with a DTI, the bearing is tight in the housing, I am holding the wheel at 3 and 9, pushing with one hand pulling with the other, (just like you do on the front wheels to check for loose bearings).I can tighten the adjuster on the wheel bearing to no end float and still wobble the wheel. Futher to this, I swapped centers back to the factory open center (single spinner)used the same axles, same bearings, same set up only now Im using 0.008" axle end float, (ONLY THING I HAVE CHANGED IS THE DIFF CENTER, WHICH THE SIDE GEARS HAVE NO MOVEMENT GO STICK YOUR FINGER IN ONE IF YOU HAVE ONE LAYING AROUND) guess what,,,,,,,, noise is gone so those suggesting its the wheel bearing, think again.