It didn't result in any drastic rolls for my region so I hadn't really had an explanation at my end, but given the timing I think there's a very good argument to be made for it representing the instability caused by the increasing use of iron, and its effect on long established tin, copper, and bronze trade routes. That even gives a good explanation for the lack of much impact in the Sunflower Coast- it had no connection to those routes at all.
Also, about the Neanderthals- I understand your reservations, the reason it's being brought up is that at an earlier stage in the project there were a lot of ideas to try to incorporate other humans into Concordia, and the one that had the most traction was having remaining Neanderthal populations kicking about in the big World Valley mountain ranges. We've been umming and erring about it ever since, so I'm also not complaining about you objecting to it. But I'm just pointing out the history of the concept with the Concordia project
As for the animal suggestions not involving Neanderthals, Pipochubs, all of those seem like plausible species and locations for them within the continent. The one thing to bear in mind about domesticates is that human activity will tend to spread them further than their natural range, and/or result in breeds that can colonise additional climates and environments. But in terms of natural ranges, all of these make sense.
There is one other thing- 13,000 TY has one more milestone. In addition to being the point at which we have complex societies emerge in the North of the Central Continent, this is also the beginning of the Neolithic in the North-Eastern continent, when crops and animals are first domesticated by the societies living there. This is why I made sure to make an extra-size map for the North-Eastern continent. This also means that we will have to pretty imminently do the same thing of mapping out some initial societies that we did with the Central Continent in advance of the history. But! We do have one major advantage- the continent is far smaller and there's only one big epicentre for agriculture, so this is not a task on an equal scale to the Central Continent. According to our most recent resource maps there are no significant deposits of tin there, so no tin bronze societies, which simplifies things a little further. The current date for 'history' beginning in the NE continent should still be around 14,500 TY. I'd rather not increase that number, because otherwise we might well end up with what looks to be a carbon copy of Columbian Exchange happening which is a) a little bit boring and b) kind of unfortunate to end up with when there are so many factors that suggest this need not come to pass. If people want to revise that 14,500 number down because we're not dealing with tin-bronze, I'd be happy with that, especially as it's entirely possible to have complex urban cultures without significant metallurgy as our planet's own history indicates. But either way, my strong suggestion is still 14,500 TY or earlier.