No, it was just noted by the journalists present. But the relationship of the prince and the departing prime minister Michel (soon to be president of the European Counsel) is a difficult one. The PM lowered Laurents dotation in 2018 out of punishment for Laurent attending a diplomatic reception Chinese embassy without the approval of the government. The prince wrote a letter in January of this year to the PM complaining about his human rights being violated by the government refusing to help him retrieve 50 million Euros from frozen Libyan funds. The PM replied in a private letter, perhaps the refusal to shake hands is an indication of the content of the letter.
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According to Wim Dehandschutter Laurent was not the only one with problems during the defile. Princess Astrid was seen 'furiously fighting' with the chef of protocol and others. He suggests that the princess may not have been happy with the placement of her seat, as she was now further away from the King than Laurent, which was an error.
https://www.nieuwsblad.be/cnt/dmf20190722_04521394