Magnus Óláfsson, king of Man - Incorrect mother?

cf https://en.wikipedia.org/wiki/Magn%C3%BAs_%C3%93l%C3%A1fsson "Although Óláfr is known to have had two wives, and no contemporaneous source names the mother of his children, Magnús' mother may have been Óláfr's second wife—Cairistíona, daughter of Fearchar, Earl of Ross, (died c.1251).[3][note 1]"