There's definitely very ugly "banding" going on in the gradients on the WebP versions i say as someone who's worked extensively with UX and interfaces.
I'm on a M2 Macbook Air.
I've read all the comments, and zoomed way in. I can see it on one of the pairs if I pay attention, but on most of them, I still am not sure how to even look for the difference.
Last time I had a vision check, I got a 20/15, which is supposed to be better than "normal". It may have declined since then.
I don't think it's a monitor or eyesight thing. I think I don't know "how" to look for the effect I'm supposed to be seeing.