Here’s the composite for a the 20 mm f/1.8 Nikkor S on a Nikon Z7 at f/4.
The top-middle, top-left, and middle-right shots are slll distinctly softer than their diagonally opposite counterparts. Is it decentering, of tilt? The way to find out is to make a series of images focusing on the star in each location. Here’s what happened when I did that, this time at f/1.8:
Most of the diagonally opposed differences have disappeared. The only one remaining is bottom-center to top-center. Therefore, I think most of this lens’s issues have to do with tilt. That being the case, I wouldn’t expect them to be a problem in most circumstances, but f/4 landscapes blown up to 40×60 would not be the highest use of this lens.