My point is there is no 'Gregorian paschalion' - that the difference between the Western (as used by Orthodox in Finland because the law says they have to) and Eastern Easters is unrelated to the Julian/Gregorian difference.
No. The date of Pascha is calculated based on three dates: 1) The vernal equinox; 2) The Jewish Passover - 15 Nissan; 3) The first full moon after the equinox and after the Passover (for the Orthodox).
For most of the Orthodox the vernal equinox date is not determined by modern astronomical science or the Gregorian calendar, it still uses the Julian reckoning which as we all know is not astronomically accurate now. There is also a dispute as to the role (or lack thereof) of the Jewish Passover in determining Christian Pascha. Finally the full moon comes into play. So the foundational difference is
still the Julian calendar.
Churches like the GOA and OCA have a mixed calendar like many other Orthodox in the world today. This causes some unforseen-in-the-Typikon combinations. The autonomous Orthodox Church of Finland uses a pure Gregorian calendar and some other parishes in isolated locations as well (where western Christians are the majority) have adopted this practice with no fanfare.
There are lots of articles on line and another message board has discussed this endlessly, I can send you a link if you like.