[mrandish]

I know from personal experience that getting one really good picture of four people when three of them are kids is quite difficult. To be clear, by "really good" I mean everyone is eyes open, looking at the camera, with a reasonably pleasant, somewhat natural facial expression and body pose. It can be done in a single photo but it can take a lot of tries - and with kids the hit rate percentage falls rapidly after the first dozen snaps. If you aren't lucky enough to get "it" in the first couple minutes, the whole process devolves into a torturous endurance session with ever-diminishing returns which can get pretty unpleasant for all involved. The longer the session, the higher the chances a meltdown or tantrum from one of kids will end any hope of getting the photo in one shot. Occasionally the meltdown is from the photographer :-).

In my case, I just composited together a handful of the very similar shots into one photo in which everyone's eyes were open, looking at the lens, etc. Because kids can't not fidget, especially when asked to hold a pose, the registration between almost identical photos taken seconds apart is often not perfect. I'm certainly no royal watcher but for a self-posted social media photo (vs some official press or journalistic photo), this seems like a pretty reasonable thing to do, if only to spare the kids a stressful experience from which they are likely to develop resentment toward official PR duties.

Applying Occam's razor, I think this explanation is far more likely than some nefarious palace scheme (in which case, I'd expect the composite to be expertly done). The fact the composite is imperfect supports the idea it was done fairly quickly by one of the parents or one of their non-expert personal assistants and not carefully reviewed by a cabal of master media manipulators orchestrating some conspiracy.