Good to see I’m not alone .
I could see the lines on the example you gave in your post.
I think i will have a play around with the CSS gradients.
On the Webflow homepage I can see the lines on the sections further down the page, however these would be acceptable. I think their gradients are more dramatic in colour changes and result in the lines being much closer together.
If that doesn’t work out I will experiment with the Photoshop examples on your post.
I actually see it not only on Safari but all browsers I have used so far. Currently I am not even on my iMac 4k but am on a Mac Book Pro Retina Display on Vivaldi browser and still able to see the lines.
For my safari issue I have found that using 2 solid colors produces a significantly smoother gradient than having a solid background with a transparent gradient overlay.