This is not true. At that time in canon, Jean and her children were destined to host the Phoenix Force like King Arthur was destined to wield Excalibur. Originally, the PF was something only Jean and her children could host until Excalibur expanded that number. Which was expanded even further during Morrison's run, and then AvX basically said, "You know what? Who cares? Anybody can host the PF," and Jean was the most suitable host for it. IIRC, the PF was interested in Jean because it found a kindred spirit in her. You will not find any canon out there post the retcon where Jean was established to be at the bottom of the bay while the PF, in the guise of Jean, "died" on the moon, where it states, "Jean Grey's full potential is equal to the power of the Phoenix Force even when she is not being possessed by it." If Jean had that kind of potential, why in the world would Mr. Sinister have been so obsessed with getting a child born of the union between Madelyne Pryor (and Jean clone) and Cyclops? He said their progeny would have ultimate power. If Jean had that on her own without the PF, he would have just stopped with the Jean clone.