The standard "great OS, needs decent editor" quip is just that -- a quip. If you look at the actual history of Emacs, you will see that the it was originally a collection of TECO macros. The first Lisp version was written by Dick Greenblatt for Multics -- it was not intended to be an operating system in its own right. The Lisp machines had Emacs versions of their own -- called EINE, ZWEI, and Zmacs. So Emacs was well-established on multiple operating systems before GNU Emacs even came along. You could say that the GNU system as a whole is intended to be a successor to ITS and the Lisp machine OS, but Stallman deliberately chose Unix as a basis because he wanted GNU to be popular and Unix was already widespread in 1983-1984.
In fact, GNU Emacs didn't even get some of its more powerful UI features until the 90s, after Lucid Emacs/XEmacs was developed by Lucid Inc. as a component of their Energize IDE -- they found GNU Emacs at the time to be inadequate from a UI standpoint, so they forked it and added the bits they needed. Most of those were implemented back into GNU Emacs, despite that Stallman thought that, for the most part, they weren't needed.
So no, Emacs wasn't designed to be a software Lisp-machine workstation. It just sort of slowly morphed into one over time.
The standard "great OS, needs decent editor" quip is just that -- a quip. If you look at the actual history of Emacs, you will see that the it was originally a collection of TECO macros. The first Lisp version was written by Dick Greenblatt for Multics -- it was not intended to be an operating system in its own right. The Lisp machines had Emacs versions of their own -- called EINE, ZWEI, and Zmacs. So Emacs was well-established on multiple operating systems before GNU Emacs even came along. You could say that the GNU system as a whole is intended to be a successor to ITS and the Lisp machine OS, but Stallman deliberately chose Unix as a basis because he wanted GNU to be popular and Unix was already widespread in 1983-1984.
In fact, GNU Emacs didn't even get some of its more powerful UI features until the 90s, after Lucid Emacs/XEmacs was developed by Lucid Inc. as a component of their Energize IDE -- they found GNU Emacs at the time to be inadequate from a UI standpoint, so they forked it and added the bits they needed. Most of those were implemented back into GNU Emacs, despite that Stallman thought that, for the most part, they weren't needed.
So no, Emacs wasn't designed to be a software Lisp-machine workstation. It just sort of slowly morphed into one over time.