I'm a republican and ordinarily this picture wouldn't be on my radar at all, but I do agree with the OP that now it's evident it's been tampered with significantly, the implications are massive. It's a piece of news media that was submitted to news agencies, who originally used it in good faith, presumably because it came from a hitherto trusted source.
What next? Would it be OK for the Downing Street press office to provide photos of the PM shaking hands with a foreign dignitary when one or both of them weren't actually present? What about a photo of him shaking hands with Stephen Yaxley-Lennon? You can't have news photos that are substantially untrue, which this one must have been to attract a kill notice - not just a little bit of photoshopping out of podge or whatever. This is a particularly sensitive area at a time when AI, deepfake images etc are rightly in the spotlight and causing anxiety prior to the upcoming general election.
It's only no big deal for the RF to have done this if it's also no big deal when the Kremlin does it.