Correct. Unless you find a promo code on the worldwide home page of ITA, then it will be valid from all departure points.

The current promo code seems to be valid only for flights from countries which have their own ITA homepage (eg the Spanish, French, Belgian, UK website - to name a few). So you can also use it when departing Paris, if booking on the French website that is. Interestingly, the discount code also seems to work only for simple one-way or return journeys, and not for open jaw tickets (not even when departing/returning from the same country on an open jaw, I've tried using it unsuccessfully for MAD-ATH-BCN).

Even though positioning to Spain instead of Greece is a bit more difficult for me in Eastern Europe, I did book a MAD-ATH-MAD ticket just for fun as a last ITA SkyTeam goodbye It's a decent MR deal - even without the discount applied - and on some MAD-FCO flight ITA uses their fancy A321neo with fully flat beds in 1-1 configuration normally used on Middle Eastern and African routes. It's scheduled on some CDG flight as well (and perhaps AMS too, although I didn't check that).