According to the Wikipedia article, it looks like more of an embrace and extinguish move, at least regarding the utilities sources and Linux development.
"However, since the Microsoft acquisition, none of the utilities currently available are accompanied by source code, and the Linux versions are no longer maintained or available.
Some of the coding tricks used were based on the Windows Native API (NTAPI), which was (and still is) mostly undocumented by Microsoft. Using these coding examples - with source - would enable developers to create extraordinary programs that performed operations that would otherwise have been impossible using a standard API. Examples include hiding Registry information, intercepting or hooking APIs to monitor file operations by the OS, as well as Registry operations."
Hmm...random person on the internet adds citation free conspiracy theory with the description of the edit as:
"Describing the non-availability of source code since the Microsoft aquisition. Under 'Source Code and Technology' header (my experience as a developer)" [My emphasis in italics]
I'd say the grandparent comment is correct when he says that "Russinovich knew the guts of Windows better than a lot of their own engineers did".
Russinovich was on the team that re-architected Windows from the ground up for the modern era.
>A few weeks ago in Los Angeles, Microsoft technical fellow Mark Russinovich -- absolutely the world's leading authority on Windows performance and architecture -- took time to explain to developers attending PDC 2009 in Los Angeles exactly what [MinWin] is. In summary, it's a way to graft onto Windows some semblance of the architectural layering it should have had, if its architects in the 1980s had any foresight into how Windows would be used thirty years later. It enables current and future Microsoft developers to evolve new configurations of the operating system, without having to rewrite core services or worry about breaking dependencies between those services and upper-level APIs.
I know about that one where the source was taken down. My favorite is Skype however where they used to use SYSENTER directly and read your BIOS using NTVDM: https://www.pagetable.com/?p=27
"However, since the Microsoft acquisition, none of the utilities currently available are accompanied by source code, and the Linux versions are no longer maintained or available.
Some of the coding tricks used were based on the Windows Native API (NTAPI), which was (and still is) mostly undocumented by Microsoft. Using these coding examples - with source - would enable developers to create extraordinary programs that performed operations that would otherwise have been impossible using a standard API. Examples include hiding Registry information, intercepting or hooking APIs to monitor file operations by the OS, as well as Registry operations."
https://en.wikipedia.org/wiki/Sysinternals