Reason I'm asking this is because I've shot my G9 viewfinder with my cellphone (aprox 28mm equivalent FL) and with a 35mm lens on a FF camera.

G9 viewfinder shot through a 28mm cell phone camera

G9 viewfinder shot through a 35mm lens on a FF camera
As you can see, the pincushion is still visible but less impactful on the 35mm compared to the 28mm.
Also, just for funsies, the DSLR viewfinder shot with the mobile phone:

FF viewfinder shot with 28mm eq phone.
Hmm, seems that my DSLR viewfinder has pincushion defect as well... even though nobody complained about it in the last 6 years since it was manufactured and I can't see any distortion in it.
In practice, I can't see any distortion on my G9, except if I really squint at minimum magnification.
That being said, I will not dismiss the whole distortion plus poor corners of the viewfinder as I had the oportunity to use an early production G9 which, even when diopter adjusted, would display visible distortion and blurry corners.
As such, in my opinion, the EVF issue was an early production issue that unfortunately got in the reviewers and early adopters hands and it got blown out of proportion.
Also, in my opinion, the G9 has one of the best EVFs on the market, bested only by the Z6/7 EVFs and possibly (as I have not tried them) the Panasonic S1 EVFs.