Hey, author here! Scott did contribute, but less than before.

On his blog he says: "I did a lot of writing for AI 2027 and was listed as a co-author. Some of my writing made it into Plan A too, but it was a bit less. The difference is of degree rather than kind, but because of this - and to give me more latitude to discuss it the way I like with less PR blowback - we decided not to put me as a co-author this time. I continue to be proud of having a part in this, small as it may be. (related: everything in this post is my opinion only, and not officially endorsed by the AI Futures Project)"