I’ve just found that the Obama Library has a considerable amount of jewellery gifted to the Obamas including Morocco, Brunei and especially Saudi Arabia. It also includes some things gifted to their daughters. King Abdallah bin Abd al-Aziz Al Saud gave the following

Ruby and Diamond Demi Parure Mouawad 2009
Pearl and and Diamond Demi Parure Mouawad
Emerald and Diamond Demi Parure Mouawad 2014

If they gave Michelle Obama these major jewels in an eight year period is it possible that they only gave Queen Elizabeth II so relatively little over many decades. I know about two demi parures and two necklaces over 70 years and two suites that have no known origin, whereas Camilla received three suites in three years. Now clearly those three years may be unusual but there has to be a lot of items that we have no clue about. They clearly gave non jewellery items but I can’t believe they were so relatively mean.

https://obama.artifacts.archives.gov/people/12683/king-abdallah-bin-abd-alaziz-al-saud/objects

https://obama.artifacts.archives.gov/search/jewelry/objects