#interix
I mentioned Guckes's list not having Heirloom vi in that other thread.
I haven't thought about these in years, and they are an understandable additional blind spot in Guckes's list; but the MKS Toolkit had a vi, as did Interix.
https://www.mkssoftware.com/docs/man1/vi.1.asp
The :open test indicates that vi in the MKS Toolkit was actual Joy+Horton vi.
#Interix (at least according to an old Scott Mueller book) had both vi and nvi, so I wouldn't be surprised if that turned out to have been Bostic #nvi by two names.
As I recall, Central Point PC Tools, the Norton Utilities, and the Graham Utilities had text editors of varying degrees but did not have vi.