Would it not make sense for Greek speakers to be found in the west?
I would suppose so. Western Iran also has somewhat more linguistic diversity than the central plateau and the east, arguably helped by the Zagros mountain system.
I am thinking of Christian Aramaic (or Armenian? but these were predominantly urban) -speaking communities, where Greek might be used as second language - these would be concentrated in Iranian Azerbaijan and other northwestern areas.
Greek settlement in the Hellenistic Age went more to the East, but is concentrated in what are now Afghanistan and Uzbekistan, and I've never met any reference to Greek surviving in those context past Antiquity.
The Ethnologue page for Iran does not list anything native that could be mutually intelligible with Greek. This story is very tantalizing but I am simply not able to relate it to anything useful.
Assuming there is actually a village in Iran where some community has clung to a local form of Greek until now, since either the Middle Ages or Hellenistic times, I would be
extremely surprised that linguists had failed to notice. They
have taken note of Abyane'i (though somewhat sloppily), for instance, and Iran is far from remote uncharted wilderness. Also, a lasting linguistic presence of Greek there would be big news, as far as academia is concerned - Greek philologists would flock to any such occasion gleefully.