Yes, it's the previous generation. Homelabbers mostly buy older used equipment at deep discounts.

There is not an EPYC 7xx4. EPYC 8004 is Siena. We reviewed an ASRock Rack Siena platform this week actually.

We had this in the Genoa launch piece but AMD largely kept $/core constant between Milan and Genoa. Milan is still being sold since it uses cheaper PCIe Gen4 motherboards and DDR4.

On the server side it takes a few quarters for new products to start making up the majority of shipments. These days it is better to think of new servers as N, N-1, and still some N-2 generations being sold as new.