That’s the thicker and heavier original iPad Air 9.7 shown in the frame above.
It’s the worst-case mass load, and the newer ones are lighter and thinner, so they’re actually easier to support in landscape mode.
All iPad Airs can work in the NanoStand, but you need to install a rubber pad for the thinner ones. It"s an adhesive-backed label, so you just peel and stick on.
DBK’s TREG unit doesn’t have that pad yet, but they do come standard with the general release.
Based on your iPad Air version, you can configure it with the rubber pad to suit your use case.