The whole purpose of shooting raw images is to do advanced processing later. However, any such processing involves creative choice which alters the image to the taste of the person doing the processing. It's easy to alter the white point and have some journalistically important details lost in the shadows.
Also in a high stakes case suspected forgery, it may be possible to detect forged images by looking at minute noise and encoding choices made by a particular camera model. Faking these details well enough to fool the experts would be beyond the expertise of most would-be forgers.
Of course, Reuters could ask for RAW files themselves and have even more fidelity/authentication potential. But those files are huge, many journalists do not have a fast internet connection where they work, and the publisher would need expertise on RAW workflows.
All in all, I think it's a reasonable decision and will be successful against unintentional/unconscious alterations and causual forgery.