>>>It seems pretty clear that the A-plot of Arpeggio did
>>>not occur in UF; in particular, the "you are the first person
>>>of Earth descent to make contact with any ship of the Fog" line rules
>>>out the existence of Gunzō Chihaya during the original Fog War...
>>...as far as Yamato and rest of the Midway detachment know.
>Iona was right there! And she never said she'd lost her memory,
>apart from the Admiralty Code.
I don't think Chihaya was around, honestly, but -something- had to have happened. The transmission about Mental Models rather implies that something happened with the Big 7 themselves--or even the Admiralty Code--that the Big 7 were not entirely equipped to deal with...such as developing emotions and opinions themselves. Since we don't know who was giving the Fog orders to begin with, any conclusions about why they stopped are pure speculation.
Given how complete the memory loss was, I'm inclined to believe it was done on purpose. It was bungled pretty badly, though. I can't imagine whoever gave the order to pack up and go really understood how incredibly dangerous it was to leave Fog ships on Earth without a command structure. Certainly, I do not expect any of the Fog ships themselves to have given such an order, with that kind of disregard for the ships left on Earth. As a result, I don't believe the Admiralty Code is a Fog ship. But again, that's speculation.
>>>and implies that Iona did not defect.
>>And yet, if she didn't defect, why was she found alone? No
>>black-marketeer would have passed up the chance to put multiple Fleet
>>of Fog ships in the inventory.
>"Extended deep-cover assignment" á la Léonne?
In truth, we know very little about Iona's circumstances. All we can know for sure is either the ship or the Mental Model was destroyed and the Union Core preserved. We don't even know which form she was in when it happened, or when. There's a 300 year gap, and it could have happened at any time.
In the anime, the I-400 series subs -were- intelligence operatives. What makes this interesting is it implies a subtlety that's somewhat contradicted by the straightforward lack of tactics they were known for in the Fog War. Is this a change of tactics late in the war? The beginning of whatever happened that made the Fog (mostly) leave? Or is it an indication that the Admiralty Code was someone who was giving orders to the Fleet of Fog without quite realizing what they were dealing with? Again, speculation. But interesting.
And, there's one very big alternate possibility, which is alluded to above with the comment that the Midway Fleet might not know about a first contact in the 21st century. What if the A plot -did- happen, Chihaya and all (with UF-appropriate modifications) and Iona's Core was found out among the stars somewhere, not on Earth at all? With the Midway Fleet's memory having been wiped, anything they say has to be taken with a grain of salt.
Lastly, I will admit that I also thought they picked up on human interaction with ridiculous speed, even realizing they've probably picked up human TV and whatnot before they ever had Mental Models. Given we know so little this early, I thought there might be a reason...what if this ISN'T the first time they had Mental Models? What if whatever affected the Big 7 spread throughout the Fleet, just like it did in the anime, and someone (Kongo is an obvious choice) resisted. Violently. By doing an inelegant mass wipe of every ship she could reach. Perhaps the ships that left wanted to take the rest of the Fleet with them but couldn't find them, or did not have the military strength anymore to reach them.
Fearless creatures, we all learn to fight the Reaper
Can't defeat Her, so instead I'll have to be Her