There is some irony on calling out benchmarks from an affiliated party and then linking to benchmarks from an affiliated party of the competing format.
> The source images were stripped of any metadata, EXIF, XMP, color profile etc. including the gAMA PNG chunk.
Just so happens that cjxl correctly supports PNG color profile/gamma data while cwebp doesn't.
I'm not suggesting to look at the "benchmark" part of this page. Given that the creators of formats can approximate the result to synthetic metrics for as long as they want, these metrics are secondary to individual perception. Personally, I would have easily sacrificed SSIM just to avoid seeing the green sand on the border of the blue and yellow areas.
> The source images were stripped of any metadata, EXIF, XMP, color profile etc. including the gAMA PNG chunk.
Just so happens that cjxl correctly supports PNG color profile/gamma data while cwebp doesn't.