Popular claim by IBM PR, but the issue was that OS2fW component (which reused locally-installed Windows 3.x) had binary patches it applied to windows core component to turn it from DPMI host (which owns 32bit pagetable etc.) into DPMI client so that Windows would call to OS/2 for handling paging setup, and other details of interop.

The patches were made for Windows 3.1, but not for Windows 3.11 - since the changes resulted in binaries with different offsets, Windows 3.11 used under OS2fW would fail.

EDIT: Source with some discussion of disassembled OS2fW code: https://jacobfilipp.com/DrDobbs/articles/DDJ/1994/9406/9406m...