They're doing that anyway because they serve non-webp images to users with non-webp-supporting browsers. Anyhow, this is the image that's for display, which is resized/compressed; they store and allow you to download the original no matter what.
I'm skeptical of this solution for other reasons, though (like that it assumes users know what JPG means).
Users who don't know what JPG means are not going to be attempting to edit the images in photoshop. Although perhaps they are saving the files to their local windows machine.
But then the jpg file will be optionally downloaded, thus reducing the bandwith usage (desired effect), and accelerating the page-load (another desired effect).
I'm skeptical of this solution for other reasons, though (like that it assumes users know what JPG means).