Hmm, this other 1979-era history of Emacs also doesn't mention Steele, though it does mention Weinreb and Moon, whom the author seems to have worked with closely: http://www.multicians.org/mepap.html.
Steele was one of the authors of the TMACS package, for which this article has “???” in the references.
Incidentally, the article mentions Multics' version of QED in passing; this regular-expression-based editor was written by Ken Thompson¹ and is a (more complicated) ancestor of ed(1), the standard text editor on Unix.
