It's more like "programming Emacs" instead of "programming in Emacs".

Try writing a mode for Emacs, something like Helm or NeoTree or Dired, in Emacs and you'll get pretty much the same experience you'd get from Pharo, although with a lot less visual feedback. Emacs is concerned mainly with text and it's naturally reflected in its APIs, but the fact that you can live-edit any function or advice and see its results change immediately after pressing C-M-x is exactly what Smalltalk/Pharo does.

It's magical, in both versions. Smalltalk was designed for GUI first, so its APIs for manipulating graphical objects are much like Emacs APIs for text manipulation: vast, rather complete, also a bit arcane due to decades of history. There's one thing that Emacs lacks and that would be support for restarting code execution from any place (possibly edited in the meantime) on the call-stack after exception: Pharo's debugger lets you do that, which is a thing worth experiencing at least once as a programmer. :)

I use Emacs, and I played around with Pharo, Squeak, and Cuis. I would go so far as to say the Emacs is an acceptable Smalltalk, but the Smalltalk environment’s defaults are far better. It’s worth playing with it to experience it (see just how good TDD can be)