Yes, but it doesn't seem to work very well. It still doesn't show spez's answers, and you could argue that the co-founder and long time CEO should use that sorting order in his own AMA where he knows full well he'll be heavily downvoted, but it seems to use the default "best".
It's turned on by default on that thread; it's just not helping much with the sheer volume of comments.
It wasn't initially; but as you noted, it didn't help much anyway.
His replies still appear to be hidden in the Q&A sorting mode.
The Q&A sort mode still shows the most popular questions at the top. The CEO only answered questions with an order of magnitude fewer votes than the top questions. The Q&A sort works fine, it’s just that no questions were answered.