Author might be right about the gradient shifts in images after conversion, but at the same time, most of the websites are not using such color accurate images everywhere. Some are logos and some are with alpha channel. It is a fact that WebPs are lightweight assets to load on the user side which reduces bandwidth consumption for the user and your server. So use WebP where it's needed to save some loading time and bandwidth and use your preferred format where you want to show images as is.

If you're planning to convert your images to WebP in bulk, I wrote a shell script: here's the link:

https://medium.com/@siddheshgunjal82/bulk-convert-images-to-...