Haha, that's totally believable and in tune with the MicrosoftMentality of those days. I'd love to see the corroborating evidence, though! If I recall correctly, the (also paid) MSDN developer reference documentation was actually pretty OK. The problems you needed Petzold and Richter for were the higher level "why is Windows this way?" topics and "what's the Windows-way to design XYZ?" questions. The actual APIs themselves had good documentation--the problem was knowing you had to use a particular API for a particular problem, which is what we needed the books for.
There's the rather famous AARD Code (https://en.wikipedia.org/wiki/AARD_code), though that is from an era a little before Win32. And, well, it's not a documentation issue for app developers, as much a way to trick OS developers.
LOL @ those memos. This was long before all our companies adopted the "Don't say anything in E-mail that could become evidence" training. Their ruthlessness and obsession with destroying everything not-Microsoft was truly unique and special. I can't think of any company here in modern times so focused on not only winning but making sure absolutely everyone else lost. Old-school Microsoft was wild.
