The date of Easter, calculated as given, shouldn't depend on the calendar.

Yeahbutİ, it's been my understanding that the Christians normalized the March equinox to some specific date (March 21?) whether it did actuallyİ fall on that date or not and normalized the date of the full moon in a like manner. The reason for the Gregorian calendar reform was that the date for Easter was drifting off from the real equinox.