I'd have to disagree. The only relationship between the Concurrent DOS which had CPM roots, and the Concurrent DOS-286 (CDOS-286) which became FlexOS was the n

I'd have to disagree. The only relationship between the Concurrent DOS which had CPM roots, and the Concurrent DOS-286 (CDOS-286) which became FlexOS was the name 'Concurrent DOS'. i.e. marketing / branding. That (CDOS-286 / FlexOS) did not eventually become DR DOS, DR-DOS developed from the old CPM-86 based thing. Both were active at the same time. I was using both between 90-97, and for a good portion of that time, both were being updated (though FlexOS moved to Novell ownership). Otherwise your description of FlexOS is reasonably accurate. The 386 version still had a 286 core, but with some modules replaced, it used the 286 loadable drivers. I was working for a company using it as a (soft) real-time multi tasking OS, with multiple processes running. The version I used no longer had the DOS support for 286 (it did for 386 - but limited), from the stuff on bitsavers, it looks like that 286 based DOS support was gone after version 1.3.