Mac Finder sort by kind is not differentiating between jpg and webp

It won't differentiate them because Spotlight sees them both with the same kind — image. If you at least want them alphabetical, then in the Finder window, press cmd+J and set the following:

This will separate your .webp images to near the end of all shown image formats because of the .webp extension name falling after .tif.

If you just want to locate your webp images, enter this in the Finder Window's search field:

kind:image +.webp

Try a restart and retest. If that fails, try a safe mode start and retest.

Start up your Mac in safe mode - Apple Support