I'm fortunate to not be as grimly cynical as this, but to take your comment more seriously than it actually deserves...
An action can be both genuine and spontaneous AND a good PR opportunity - they're not mutually exclusive.
I think it's quite possible that Catherine has matured and grown in confidence over the years - she's now in her early 40s - and feels more at ease and able to be her more relaxed self when inter-acting with people. I imagine in the early years she was very nervous and more focused on not making a faux pas.
She's also a mother of 3 young children and I know that for me (not an obviously maternal person) that gave me huge empathy with children and parents that I hadn't had before. She's probably much more attuned to what children are doing and what they want.
She's been through a tough year and has had a brush with mortality (and we don't really know what the current situation is regarding that). This can give you a) a clearer picture of what's really important in life and b) an 'I don't give a damn - I'm going to do what I think is right even if some people might tut' attitude.
So I think your comment was mean-spirited and very reductionist.
I hope your life is nicer than this comment makes it sound!