No, this is wrong. They are merely the only country that starts Christian and can raid straight-way. Becoming a Pirate Republic is not linked to religion, and is eg very easily available to the Irish minors. Forming Morocco, Tunis, Algier or Tripoli is also not tied to religion, you just need to culture-shift.
Since Ireland has bonus Republican Tradition in their NIs, flipping to pirates and then forming Ireland is a good choice IMO.