Dave,
To answer your question: The aluminum alloy Peerless uses for their transaxle cases has a small amount of silicone in it so that the aluminum bore that the axle rides through is actually a "bushing." Most OEMs don't want to pay extra for bearings, so they specify no-bearings, and the aluminum alloy works fine for light-duty lawn mowing.
I also notice that the bearings in your picture look like ball bearings. Peerless also offers needle bearings for these axles for better load-carrying capabilities.
Respectfully,
Rodney Rom
Peerless Gear Master Technician
Rom's Reworks
Butler, MO