What, you mean this hub?
There are two sets of bearings in the cassette body. You just can't see the inner one on that pic. The red bearings are the only ones supporting the hubshell (yellow). The green cassette body sits independently on the axle and only interacts with the hubshell via the freewheel pawls.
It should be clearer on this much better pic I found in that old catalogue and scanned instead of taking a lousy phone pic.
Pretty much every hub that isn't an IGH or coaster brake has four bearing races; two for the axle and two for the freewheel mechanism. Shimano,
AFAIK, are the only ones to put the drive-side axle bearing next to the dropout, where it belongs.
Campy started with a hopeless fail of a design, and engineered it to work. I'd much rather start with a design which I can't imagine significantly improving.