Sometime around January, WAFA changed its style guide. Because now, virtually every similar article describes them as "colonists," not "settlers." See this story from May:
Someone, probably from the PLO, decided that "settlers" just didn't have that visceral effect that they wanted. "Colonists" sounds even more illegal.
Similarly, "settlements" have morphed into "colonies."
While I haven't seen them use the term this way, it could be that they prefer "colonists" because they can use that word for Israelis on either side of the Green Line. Hamas calls all Israelis "settlers," perhaps the PLO wants to reserve the term "colonists" as a rhetorical tool against all Jews.