If we made a list of things you could do, that would be on the list.

If that's the only thing that changed, the data in the file isn't changed, it's still a webp file not a jpg, it's just mislabeled now. I just tried it, Dolphin will let you do it but throw a dialog telling you it's not actually going to change the file, just the name. Some systems might be smart enough to recognize the intent and run a conversion program in the background. Feels like an Apple thing to do. Also feels kind of Pythonic.

A lot of image viewing software doesn't know what to do with the webp format so they'll try to load it and throw an error.