I have read a lot about that time and it doesn't seem particularly biased. Microsoft hated working with IBM and their horrifically old-school way doing software development (e.g. counting lines of code, etc).
The bias, in my opinion, is the other way -- which is exactly what I said at the top.
Letwin says what killed OS/2 was that it could run Windows apps.
This is not true.
That only applied to OS/2 2; OS/2 1 could not run Windows apps.
It didn't matter; there weren't any.
Windows apps followed Windows 3.0. Windows 3.0 followed the failure of OS/2 1.x.
This is his bias: he was one of the project leads and was passionate about OS/2, which blinds him to the fact that it was OS/2 1.x that flopped and there was nothing OS/2 2.x could do to usefully come back from that.
His assertion is that 32-bit OS/2 flopped, because it lacked native apps, because it could run Windows apps. This is not true.
It flopped because Windows 3 was out, and Windows 3 was a hit because it did what 16-bit OS/2 failed to do: it ran DOS apps _well_ and it could do that because it took advantage of the 386 chip.
His bias means he fails to identify the true cause although he named it.
Secondarily, I think we can point to a 2nd, non-technical, personal reason: Letwin was not involved in Windows 3, which was essentially a 1-man skunkworks project.
So your responses don't seem to be addressing the issues I raised.