The lower-end ($999) M75s SFF has, uh, an impressive markup. 256GB SSD, 8GB RAM, and only integrated graphics. An ASRock A300 will get you there for about $150 (the case/mobo/PSU/wifi) + $100 (the 3200G) + $65 (500GB WD Blue NVMe, an upgrade!) + $35 (8GB laptop RAM) = $350. Assembly will cost you something but you can probably work that out if it'll save you $650 a unit. I know, big customers get discounts, some need the management features, businesses will pay lots just for support and like to use their chosen vendor(tm), but even considering all that, wowie.
Why make guesses that are counter to not only what we know about A300 and X300, but things already discussed in the article? (Besides the fact that I guess that statement can unwittingly kind of true if you choose to not use an APU, since the Ryzen CPUs include a chip very similar to the X570 chipset in the form of the I/O die...)
The A300 and X300 "chipsets" mean the motherboard is built for an SoC CPU/APU without an external chipset. Ryzen has some SATA and USB on the CPU/APU itself, so those can provide the needed connectivity for low-cost or small footprint systems.
If you check the connectivity listed, it matches that provided by the CPU - as long as you repurpose the 4 lanes usually used for a chipset for an extra M.2.
I would assume that AMD design rules for X300 - similar to the how the distinction works between the higher end X, B/A series chipsets - allowed bifurcating the primary x16 connection to x8/x8, while A300 didn't. (Although this doesn't really affect things much since most systems like this would be equipped with an APU that has only 8 lanes for the GPU to begin with.)