Focus curvature with the 20mm f/1.8 Nikkor S

I used the quick-and dirty focus curvature test (Photoshop > Filter > Stylize > Find Edges) on a picture of my driveway with the 20 mm f/1.8 Nikkor S wide open on a Z7.

There is some focus curvature, with the focal plane bending toward the camera as you get further off axis. The Sony 20/1.8 G lens exhibited similar behavior.