> There was no MS-DOS 5.11.
There was Windows 3.11 which ran on top of MS-DOS 5.0, the two numbers probably got mixed in their memory.
There was also an MS-DOS 2.11.
There was indeed a Windows 3.11 and the much more common Windows for Workgroups 3.11 which was a profoundly different product (32-bit disk subsystem & 32-bit networking subsystem -- the first time these pillars of Win9x went out into the world.)
But neither of them ran on any particular version of DOS. They ran on PC DOS, MS-DOS and DR-DOS -- although Microsoft tried very hard to block the latter:
https://en.wikipedia.org/wiki/AARD_code
They ran on DOS 3.3, 4, 5, 6, and 7.
There's nothing at all that links them especially to MS-DOS 5.
It is. Because:
> but I feel like MSDOS 5.11 was where things finally just worked
There was no MS-DOS 5.11.
It went 4, 4.01, 5, 6, 6.2, 6.21, 6.22.
IBM had a few extra versions as the divorce was occurring at the time.