"Not necessarily. While IBM supplied the OS/2 specs and change requests as MS was doing the coding, MS reportedly had a "secret" project going on, which was Win95. I think it came as a total surprise to IBM ESD, which was wondering about MS' performance just before they took OS/2 development back in-house." - Techjunkyard
Here's where the conspiracy theories again break down: software ran at the same speed under Os/2 as it did under Windows 95.
If there were "secret hooks" and other such shenanigans written secretly into Windows 95, then the competitors affected by such tricks would have gone to court and shown the judge and the jury their software (e.g. WordPerfect) running dog-slow under Windows 95 versus rabbit-fast under OS/2 in a side-by comparison that would have been difficult to defend against at trial.
So it's pretty tough to get me to accept the whole secret conspiracy by MicroSoft argument.
Broadly speaking, IBM was privvy to the Windows 95 code base, the performance for Windows 95 and OS/2 is generally equal, and U.S. copyright law would lend weight to all of the above source code being stored in the Library of Congress. Those are all hurdles that the secret conspiracy crowd would have to overcome to be believed.