I get the idea that this is how it was made for Queen Frederika. The base lifts the diadem a little bit, which was necessary with Queen Frederika's more bouffante hairdo.
On the flat hairdo of Princess Marie-Chantal the 'lift' was totally unneccessary. Ach ja... does not mind, she was the star of the evening anyway. Everybody is focused on Marie-Chantal and no one anymore on the Jubilee Girl...