i do remember the initial promo on Perl6, where an assembly language of sorts, called Parrot

Parrot is a virtual machine; the assembly language is called PIR (Parrot Intermediate Representation). But it's not essential for language interaction. The important concept is that parrot knows about common concept in dynamic programming languages (like subs, methods, strings, integers, other numbers, conversion between types, namespaces), and thus allows you to call methods on foreign objects.

Since Perl 5 was never ported to Perl 6, I don't see how parrot relates to the statement that Perl 5 is a poor assembly language.

...whatever happened to the dream of the Grand Unified Language ?

That's still alive, and in Rakudo you can eval() Ruby code, and load Ruby libraries - to the extend that they run on the ruby compiler for parrot, which is quite limited right now.