Do you mean the actual packaging of silicon dies and putting them into DIMMs? Yeah, they had to revert back, but that's because a lot of the memory silicon that's only good for DDR4 never shut down, and any silicon memory that is good for DDR5 is also getting claimed up for non-DIMM memory (e.g., memory packaged with logic chips rather than sitting on its own package in a DIMM or even soldered to the board).

Basically, previous generations' silicon fabrication tech is still going, and there are still buyers of that last generation product.