Realize you are somewhat summarizing, but:

"compatibility with unix" didn't matter in those days.

There were many, many OS's, all running on computers so expensive (for whichever micro/mini/mainframe segment) that most people didn't expect to replace them, ever.

cpm vms tops10 tops20 unix multics rsx11 mvs os/360 gcos apple dos etc etc etc.

The article mentions Xenix, to be more specific.

I know we all love bagging on Microsoft, but insisting on backwards compatibility with the system you're directly replacing is not an unreasonable decision, especially since changing it could well have made DOS 1.1 scripts silently destroy data when run in DOS 2.0.

That's what the lesson here is about, I believe. That a reasonable decision in the short-term can be unfortunate in the long-term.

Taking lumps for a few months when the userbase was miniscule compared to what it is today sounds more reasonable now.

They were actually bagging on IBM which occurs less often but is probably equally loved.