When AMD launched the X570 chipset last year, the chipmaker made it pretty clear that the corresponding motherboards wouldn't support the first generation of Ryzen processors (codenamed Summit Ridge). Some X570 motherboards have been found to work fine with a Ryzen 1000-series chip, but that's stepping into a grey area, and you're running it under your own risk. This begs the question of how Gigabyte was able to circumvent AMD's impediment with the Ryzen 5 1600 AF and Ryzen 3 1300 AF? The answer is evidently hidden inside the silicon itself.
Despite the fact the Ryzen 5 1600 AF and Ryzen 3 1300 AF carry the Ryzen 1000-series branding, AMD doesn't make them with the same ingredients as the vanilla versions. The original models were based on AMD's Zen microarchitecture and fabricated with the GlobalFoundries 14nm manufacturing process. The AF models, on the other hand, hopped on the Zen+ microarchitecture and 12nm process node.
In case you've forgotten, that's the same combination that AMD utilizes for the Ryzen 2000-series (codenamed Pinnacle Ridge) chips. Even though AMD might not officially confirm it, the Ryzen 5 1600 AF and Ryzen 3 1300 AF are essentially underclocked versions of the Ryzen 5 2600 and Ryzen 3 2300X, respectively.
The Ryzen 5 1600 AF and Ryzen 3 1300 AF might not be official members of the Pinnacle Ridge family, but they meet all the requirements. As a reminder, AMD still supports Pinnacle Ridge parts on the X570 chipset so, technically, Gigabyte isn't breaking any of AMD's rules. As a matter of fact, AMD is aware that these AF models work on most X570 motherboards and is fine with it. Sadly, AMD can't guarantee that processors will work without a hiccup, which is why the chipmaker doesn't publicly advertise it.
More recently, AMD broke the news that the 500-series chipset is ready for the future Zen 3 processors. However, the chipmaker's stance on Summit Ridge remains firm as the chart revealed that B550 chipset only supports Ryzen 3000-series (codename Matisse) or newer chips. As a result, support for Ryzen 1000-series AF models will not translate over to the B550 chipset. Without proper support for Zen+, the B550 motherboards will never welcome the Ryzen 5 1600 AF or Ryzen 3 1300 AF, officially at least.