The early history of EMACS is a little more complex
that what you paraphrase
from the XEmacs docs. According to folks at the AI Lab at the time, RMS
went around to every single user of ^R mode in TECO (which he had written)
and collected all of their personalized macros, then rationalized the table
of assignments. EMACS is far more than just "a merger of TECMACS and TMACS".
There's just one line about Multics Emacs in the XEmacs doc, in anyone
wants to know more about that particular version there's an
interesting article by B. Greenberg which describes it all, and also
talks about TECO and ^R mode and how that lead to the switch from what
was TECO to Emacs. The article is at
http://www.multicians.org/mepap.html
-Tor