Also, the blog post buries the lede somewhat. I found that this was the most important bit:

    Update: Turns out the “unexpectedly positive” was a reaction to day 3, 
    which covered pre-IUT material. Today, when things turned to the IUT stuff, 
    it did not go well at all. See the link in the comments from lieven le bruyn 
    to a report from Felipe Voloch. Unfortunately it now looks quite possible 
    that the end result of this workshop will be a consensus that the IUT part 
    of this story is just hopelessly impenetrable.

So while there was an early sense of optimism that the gathered mathematicians would be able to find some way through the papers at the beginning of the week, it seems that optimism has soured as the week progressed.