It is interesting that Prince Jean's wife Diane's last name is listed as of Luxembourg, given that the grand-ducal court identifies her since 2012 as Countess Diane of Nassau. I believe there are three possibilities: 1) Princess Astrid and Ralph Worthington disagree with the Grand Duke's choice to award Diane a lesser title than her husband, 2) the Grand Duke has at last created Diane a Princess of Luxembourg, or 3) the guest list calls the guests by the names they use for themselves (and Diane has always used the title Princess of Luxembourg, without the blessing of the Grand Duke). I am inclined to believe in the third option.
ETA: Also interesting is that the guest list uses of Nassau and not Willms for Princess Marie-Gabrielle of Nassau. The position under the both the house laws of the House of Nassau and the civil code of Luxembourg is that the legal surname of married princesses remains "of Nassau", but every other princess of the blood has used her husband's last name.