Lar's comment about Richie and Stan having worked on a PDP-8 version sounds reasonable.  I don't know Stan's full story as I never worked with him closely, but Lorin Gale hired Richie and Jack into DEC out of Brooklyn Poly to work on the PDP-12 in about 1972; where they had been PDP-10 hackers as students/roommates (and nearly 50 years, multiple children and marriages later, still nearly inseparable/often hard to tell apart).

Anyway, the PDP-8 was the development system for the 12.  So Richie wanting a more compatible TECO would be something he could/would have created.  

My memory is that TECO-8 was sort of like the PC's micro-emacs in that is was written in the key/model after it's namesake, using TECO-10 in syntax and commands, but very limited and much smaller and could run on a more resource limited system.   It was certainly true for TECO-11 the PDP-10's macros (EMACS) would not work there and I think the same was true for TECO-8.

That said, I did not mess with either enough, as I came late the PDP-8/12 work, and really started with PDP-11s and Vaxen.   So we would need to talk to a few people a little older, like Richie or Jack Burness who were there.

Clem