Not sure. I think the Danish Royal Family was clever to make a jewel pool which they they can lent or borrow if the need arise. I think that was because the bulk came through from the inheritance of Queen Lovisa (wife of King Frederick VIII). Indeed the continental royals wore much more jewelry than the British ones. I think they enjoy seeing their royals looking like one and proud of them, while there is a class system in Britain that is jealous of finery. The last one to use clothes and jewels to win popularity was Diana, and maybe the Queen wanted to limit Kate's expose as she did not want the young woman to overshadow her. I agree that was the Queen's intention to limit the jewels to only the ruling branch of the family. I think it makes sense now, as events seem to indicate that it is possible that the story that the queen asked "where are the jewels ?" the night Diana died might be true.
In Denmark there are only a few jewels in a fouindation and these can only be worn by the Queen. The same for the Crown jewelswho are on dislpay at Roseborg Castle. All other jewels are prvate owned.
For example from Queen Ingrid's jewels she left her ruby Parure to Crown Prince Frederk, a plamette heartshaped tiara and a turqiose tiara to Queen Margrethe II., a pearl and star tiara to Princess Benedikte and the Cartier Khedive tiara (worn by her daughters and graqnddaughters on their Wedding days= to Queen Anne-Marie.