I cannot understand the hoopla. Notice it wasn't captioned "Look how well I'm recovering," in which case you'd expect a recent photo. No, it was captioned "Happy Mother's Day", which means all it is is a snap of her and her kids that could have been taken any time and posted to mark, wait for it, MOTHERS DAY. Not RECOVERY DAY.
The royals frequently use pictures from past events or photo shoots to mark current occasions. For example, their Christmas card photos are often taken from events that happened earlier in the year. So why does this have to be different? Why can't she just post a family snap for the holiday like millions of other people did?
I think all she wanted to do was send a shout out to mothers. I don't even think it was to quell the recent rumors which, IMO, are nothing but a bunch of people with nothing to do just tossing stuff into the void to see what they can get to stick for points on social media.
Nothing is as sinister as all that. And as far as the editing, so what? Maybe there was a fly or a distracting beam of light or a thread hanging loose or a spot of dirt. Who cares? The woman had surgery, is recovering, updates are being provided on the schedule announced at the time (so, none, since nothing significant has happened), and that's all the world needs to know.