The "tradition of Smalltalk" is to experiment and exceed what came before. Alan Kay expressed disappointment about the ossification of Smalltalk upon the release of Smalltalk 80. Pharo and Squeak are trying to carry forward only the tradition of the original Smalltalk to produce new ideas, not "be a Smalltalk" (whatever that means).

If you say "Pharo is a Smalltalk" then you might get some of the religious elite come and claim "Thou must change this aspect of the system! For it is in violation of the law of Smalltalk as handed down to our forefathers in Smalltalk 80". Pharo is its own system, heavily inspired by Smalltalk to the extent that non-language lawyers look at it and say "it's Smalltalk".

People argue about whether Janet or Clojure are lisps. Some people say that only Common Lisp is Lisp. Some include Scheme as well. But the unqualified "Lisp" usually means Common Lisp when referring to an actual language with an actual specification that you can find an actual compiler to create binaries with. Pharo is a Smalltalk in a similar way to how Scheme is a Lisp. Different enough that saying "Scheme" means something different from "Lisp" to everyone who knows enough to know what you're talking about.