Demos for a couple old versions: https://www.youtube.com/watch?v=NqKyHEJe9_w Demo for Pharo: https://www.youtube.com/watch?v=baxtyeFVn3w
Interlisp-D, Mesa (XDE) and Mesa/Cedar, all shared same ideas with Smalltalk, regarding developer tooling.
Same on Genera with Lisp Machines.
Smalltalk's from the 70s and 80s, and almost certainly had what you're thinking about given it's where both Microsoft and Apple got their foundational ideas (restricted to significantly less powerful hardware), and later unrelated smalltalks retained a lot of now quirky considerations and behaviours. Self inherited a lot of those and is from the late 80s.
So yes, I was also expecting the author to talk about Smalltalk.
The second paragraph says: "This time around, I want to look at the pure text-based IDEs that we had in that era before Windows eclipsed the PC industry."