As of this post there isn't an official response by AMD, but the most plausible theory is that they are actually duff Ryzen 2600 chips and they're rebranded as 1600 so they can be sold.
https://www.tomshardware.com/news/thats-ryzen-af-some-old-amd-chips-might-be-getting-a-12nm-makeover
Original, AE code
Revised: AF
