I did look at that page and see nothing is showing up as WebP. If you want someone to dig deeper, you can open a Support ticket: Login to Cloudflare and then contact Cloudflare Support by clicking on the Get More Help button.
I took 5 random images and converted them using an online JPEG to webp converter. All were reduced in size around 30-50KB.
I also want to add that even using Google page speed tool, Google present four images and shows potential reduction in size based on processed images. Which shows that those three images, which I checked myself, can be further reduced in size using webp.
The presence of “status=vary_header_present” in the CF-Polished header indicates that the Vary header may somehow be affecting the processing of Polish (though I haven’t seen this documented anywhere, and it’s not listed as a common CF-Polished status here.).
I’d try to remove (unset) the Vary: X-Forwarded-Proto header and see if that does the trick. And if so, let Support know about this. (If it’s not a bug, they should update their documentation)
Do you have an example link? Or links to the images? I wouldn’t mind comparing.
Keep in mind, there is LOSSY and LOSSLESS conversion option. Google might be presenting a lossy version. I have tested lossy vs lossless, and you might be surprised how little loss of quality there is in lossy mode, yet file size is decreased substantially. You will get a MUCH HIGHER webp conversion hit rate with lossy mode, because the converted images will most often be smaller than your original JPG’s.
Conversion rate will also depend on the compression of your original JPG’s. If your JPG’s are already compressed optimally with a modern JPG tool, WEBP will struggle to beat the compression for most images. The exception would be in “lossy” mode, in which case it will likely find file size improvements, but this will also depend on your original images.
I have TWO websites using Polish, one in lossless mode and the other in lossy mode. The website in lossless mode converts few images to WEBP, because my original JPG’s are already optimally compressed. The website in “lossy” mode is for screenshots (dropshare), and offers big reductions in file size, especially for PNG type images (which WEBP does much better at a fraction of the file size). I don’t like the idea of “lossy”, but I am considering changing the “lossless” website also to “lossy” after studying the results.