That's really it, I think; not only about the books, or where the expedition goes, but pretty much everything about the worldbuilding. Vibrant; beautifully illustrated; interesting characters -- but the worldbuilding is in general just not thought out at all. Detailed, worked out information's given for isolated bits and pieces; but info given in one section doesn't match what happens in other parts of the story; and coherent background info for how either the human societies, or the ecology, or the Rash itself works is just nonexistent -- and I think not because Minna understood it but didn't get to explaining it before changing her belief system, but, I think, because Minna thinks and thought that it doesn't matter, and therefore either never bothered working it out or deliberately didn't work it out so that a coherent spelled-out framework wouldn't interfere with what she wanted to do with the story at any moment.
Thorny, I think it was a bit of all of your suggestions. Towards the end of comic she was repeatedly surprised in the streams about questions people had, and mentioned that if she ever was to do a long-form story again, she will have to set up a register for herself to keep tabs of the references, foreshadowings, ideas and world building things. So partially it seems that she just didn't think 100 % coherence is important, or alternatively thought she can keep it all in her mind and only realized after the fact that she couldn't.
A lot of it was about her wanting to leave room to make up things. She did say, she doesn't want to "paint herself into a corner" so either chose not to make references to the future (even where we thought we saw some
) or then just disregarded them when she changed her mind. The great green omen both Reynir and Lalli saw was one such thing she mentioned. She had planned for omens to be an important feature in some story, but she later abandoned it so that one scene became kind of random. Which reminds me that I haven't read anything about it - I suppose everyone was waiting for whatever the omen predicted to happen in canon, and then it didn't, and now it's a bit forgotten. But now it's in the "public fanwork domain"!
Also based on her comments during the prologue and later in the streams, it seems she has done a lot of work for some areas of the world building. We know she has studied historical pandemics a lot, and she spent a lot of time designing the world map and the settlements, and scouted out many areas (she went to live in Mora for this reason!). But then for some others apparently not much planning at all. I was trying to make some questions about the magic systems but it sort of looked like there is no system. So decided against it - I don't want to get some silly answer like happened with the discussion about Emil's mom.
Earlier someone else was asking about governments in the various countries, and she handwaved it saying that the villages are self-governing but there are not central governments. This cannot possibly be the case as the countries have militaries and national scale projects.
The same goes for ecology. The schemers cut food budget stating that the crew will have to hunt. Also in response to a question about what trades are included in the "peasants" category she mentions food hunters. But at least in Silent Denmark healthy animals seem to be very rare and the only references to hunting for food are Emil not shooting a deer, and the one squirrel Lalli drops into the pot. Not only that but they also talk about how sometimes enclaves of healthy animals may be formed in special places (which Mikkel would know how? By having been in the Silent World before?)
So, I have to conclude that she did after all bite off more than she was able to chew. Being one person producing pages at the speed of light didn't leave enough time to work things out as they come along, so some of the pieces are sticking out in weird angles. This is not meant to downplay her achievement at all! This was the style she decided to work in, and it got us a beautiful wealth of stories. Her decision to just wing it with some (many) things about the world was hers to make. Now it's up to us to fill those holes