The evolution of Proto-Greek should be considered within the context of an early Paleo-Balkan sprachbund that makes it difficult to delineate exact boundaries between individual languages. The characteristically Greek representation of word-initial laryngeals by prothetic vowels is shared, for one, by the Armenian language, which also seems to share some other phonological and morphological peculiarities of Greek;
What progression coincided with the the early Greek states that makes it difficult to give credit for the language and differences ? 
Paleo-Balkan sprachbund that makes it difficult to delineate exact boundaries between individual languages.