Very good point. I think they might be comparing a photo of her standing for an anthem to a photo of her talking to a guest...two totally different things that call for completely different body language. And of course her jewelry and orders are more up to the Queen than up to her. Also the “pretty princess” gown is actually better suited to her body type as it helps to balance her wide shoulders and narrow hips.
All that being said...of course someone would be nervous at their first state event.
One of my complaints is that because she (and William) was so coddled it’s taken far longer for her to get comfortable. Nine years and she’s only attended 4 of the 14 state visits and 6 of the 10 diplomatic receptions since her engagement. The BRF need to understand that there’s a difference between throwing someone into the deep end unsupported, coddling fully grown adults, and offering proper support to accomplish age and position appropriate goals. Had they done so then perhaps Kate would have shaken the nerves by 5 years rather than by 9.
While I agree in theory, I can see why, at least in part, The BRF handled Will and Kate like they did. As you said, Will was coddled, and I will add spoilt, most of his life. He would have been so even if certain events in his life had not transpired. That led in a large part to William being let have his own way in how much he and by extension Kate, would work. Treated him with kid gloves and walked on eggshells around him, they did. Second, there were complications, large and small with three previous married ins, not counting Tim Lawrence or Autumn Kelly. I think they very much wanted no problems whatsoever with W&K, and so let them make their own schedule.
If Will had been of a different temperament, less spoilt and less stubborn, we'd have seen Will working more before and after marriage, and Kate be eased in on a faster timetable.
This is a number of reasons why William, and by extension Harry, were given such a slow introduction to full-time royal work:
1. They weren't needed as there were plenty of royals able to do the work
2. The belief that if Diana and Sarah had had the chance to be more 'just a wife and mother' for the first five or so years of their marriages they may have had a greater chance of success
3. The fact Diana died - and left the princes extremely wealthy men and so able to leave the BRF if they so wished ... by marrying without consent and so any subsequent children would be illegitimate (the new act makes it so that the marriage is legal and children legitimate but out of the line of succession in perpetuity while the old act said that the 'marriage' wasn't a real marriage and any children were illegitimate and so still out of the line of succession)
4. The fact that both The Queen and Charles had been forced into royal duties while still trying to be parents of young children and they both felt that the 'family' side of their lives suffered as did the children. They didn't want a repeat if possible.
5. Basically The Queen and Charles looked at what the past generations had had happen and what had gone wrong as a result and so were determined to let things happen differently for Charles' sons in the hope that the sons would end up in better marriages and also be more supportive of the family