Which version of Minix did they actually use? There is Minix v3.1 (released in 2005 with the book), 3.2 (released in 2012) and 3.3 (released in 2014).
And which version, I know it’s MINIX 3 but beyond that? No idea. They probably heavily modified it and as Minix is not GPL, Intel never published it. Based on the timelines it’s likely 3.1 as the ME platform has heen around since approximately 2007 iirc.
Then I guess it's one of the 3.1.3x versions released in 2007 (see https://github.com/Stichting-MINIX-Research-Foundation/minix...), or maybe 3.1.2 from 2006, depending how long hey had to implement the ME.
Sometimes I wonder how the world would be today if MINIX was distributed with a FLOSS license similar to Linux. I think the Linus Torvalds vs Andrew Tanenbaum debate could have been a pivotal moment in tech history by the way MINIX missed a huge opportunity to step up in the history.