As DR-DOS 5.0 owner, it run Windows 3.1 just fine.

You are referring to Windows 95 trick from Microsoft, regarding DR-DOS 6.

I think you are probably referring to a beta of Windows 3.1 which deliberately barfed if run on any version of DOS that wasn't MS-DOS. That code was never included in any final non-beta product.

Windows 95 doesn't care what version of DOS you have because it replaces it with its own - MS-DOS "7.0".

I don't think Windows 95 could run on any other dos without a lot of hacking and highly specific expertise?

Second part of my comment.

This book has the background history about it, if I remember correctly.

https://archive.org/details/unauthorizedwind00schu_1

And there was the whole court case.

https://www.wired.com/1999/06/more-legal-trouble-for-microso...

I see. I ran a version of DR-DOS that wasn't compatible then.