He already did that.
In an alternate universe that no longer exists. (That is, Ch. 109 is different now.) I do agree that a retcon is involved makes that less probable.
But in the intervening minutes I've thought of a better explanation: Voldemort is thinking about a new and difficult subject, and that's consuming enough of his attention that he is making general errors.
Overall, the plausibility relative to the alternate theories--that Voldemort is pretending to lose--is indeed low. But given the fearsomeness of an intelligent Dark Lord, basically the only hope that Harry has is somehow surprising Voldemort, and this surprise seems more plausible than a partial transfiguration surprise.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 111.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: