>Given that Intel doesn’t have any processors (aside from the Stratix 10 FPGAs) that support the PCIe 4.0 interface, the developers obviously don't have access to an Intel-driven test platform with the new interface
Beyond that, Stratix 10 is "shipping" in the sense that low-volume samples are being distributed to large partners, but it is practically impossible for anyone to buy a Stratix 10 in any formfactor other than dev kits.
And the non-$10,000 dev kits don't have PCIe 4.0.
The article is obviously about the lag Intel is experiencing with getting PCIe 4.0-capable products to the larger market.
You can get Zen 2 and POWER systems with PCIe 4.0 today, and it is highly likely that ARM-based motherboards supporting PCIe 4.0 will be available on the general market for actual purchase before Intel releases something.
One-offs, samples, test gear, and dev kits don't "count".
If they did, then PCIe 4.0 was first "available" in early 2016 because engineers got their first PLDA dev kits which allowed them to start prototyping their designs.