Thanks for the many delightful clips and pics.
First Frederik and sitting down. Alas, Wartenberg is right.
My first thought is Frederik having a case of brain-fog - happens to everybody at times. I also imagine, without making any excuses, that the general mood for this visit was akin to being with family and friends. I.e. it was more relaxed and people were perhaps not as focused on formalities. And that's when things like that can happen, they shouldn't, but they can.
However, it is indeed such mistakes that
some royals are punished very severely for making. Especially royals who marry into the royal roadshow. I think we all know how it is to be nervous, and you really want to make a good impression and do everything right and then you end up doing the very mistake you didn't want to make. - It doesn't exactly help if the person making the mistake is already picked on!
Another detail. Dannebrog sailed in front and arrived in Aarhus
before Norge.
It's all according to protocol. Denmark in the shape of M&F were the hosts, so they had to arrive first in order to receive their guests.
Otherwise the Norwegian Regent Couple would, so to speak, be left stranded and the quay, peeking over the bulwark asking: Where are they? No one to welcome us? Are we supposed to stay here aboard Norge for a week or two? Did we arrive at an inopportune time? How about we just walk down the landing now? That'll teach 'em! - You get the drift.

It's to avoid all that, that Dannebrog arrived and moored as the first ship.
Also, Frederik has to inspect the honor guard and formally take charge before greeting the honored guests from Norway. Or in this case say hi to the people who showed up to say hi to the Norwegian guests.
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ADDED:
There were a few problems getting the landing in place at Norge, but finally it was done, so that the Regent Couple could be received by M&F:
https://imgproxy.jyllands-posten.dk.../ALTERNATES/master-3_2/royalt-besoeg-i-aarhus
Aarhus municipality also presented the Norwegian guests as well as M&F with some... ehhh... unique... presents. Made in quite some haste. The potmaker making them was only told in May, so she got busy and there was no second try when making these... items.
The one to the Norwegians:
https://imgproxy.jyllands-posten.dk...h0c/ALTERNATES/master-free/norsk-kongepar-jpg
And M&F's present. I'm sure they can find a good spot for it somewhere - in an attic.
https://imgproxy.jyllands-posten.dk...ALTERNATES/master-free/dansk-kronprinspar-jpg
The return dinner was aboard Norge in Aarhus harbor yesterday as you can see in this article:
https://www.tv2ostjylland.dk/aarhus...e-skulle-til-frokost-og-blomsterpigen-i-skole
The flowergirl Vera, was busy. She was to present the flowers and then it was off to school.
https://www.tv2ostjylland.dk/aarhus/vera-gav-blomster-til-kronprinsessen-og-saa-videre-i-skole