Are they really her 18th birthday gift?

According to BilledBladet's article the Pearl earrings worn by Queen Margrethe on 30th August when she inaugurated this year's Aarhus Festival were a surprise gift from her father on her 18th birthday.

The article (in Danish only I'm afraid):

https://www.billedbladet.dk/kongelige/danmark/oereringene-gemmer-paa-en-soed-familiehistorie-og-et-stort-oejeblik-til-festugen

An older photograph of the Queen, then Princess, wearing the earrings:



However, I have had a closer look at the "evidence" concerning the earrings and I do have some reservations when it comes to the statement that these were given to the Princess on her 18th birthday:

https://wordpress.com/post/regalevents913271078.wordpress.com/6770

The BilledBladet article cites the book "En Dronnings Smykkeskrin". Has anybody read this book? I have no doubt that it is a serious work, but if you have read it what did you think about it?