Got it. Quora post is suspicious. That said windows is a lot of machine code. It is more than plausible. NSA is known to have an active relationship with Microsoft.
If 9/11 == inside job is say 2/10 plausible this Quora speculation like 7/10 plausible IMO.
I was responding to the Quora link (where the question was "is there any evidence for backdoors in Windows or other client software for the NSA/CIA?")