Why does the nut move inside the cage?
The inner nut is deliberately allowed a small amount of movement so the screw can find and align with the thread even when the equipment ear and rack hole are not sitting with mathematical perfection.
A floating nut is useful; a nut wandering about like a loose shopping trolley is less so. The Premium version retains that alignment freedom with noticeably less movement than the Standard version.
More from M6 cage nut basics
Explore related questions about m6 cage nut basics.