From the same article you reference: "[Mary] in the first instance of her conception, by a singular privilege and grace granted by God,
in view of the merits of Jesus Christ, the Saviour of the human race, was preserved exempt from all stain of original sin."
It is because of Jesus Christ that Mary was preserved (all for the sake of His glory), and not by any merit of her own. There is no contradiction.
Which again is found NOWHERE in Scripture and contradicts Scripture pas previously noted.
And the RC doesn't want to appeal to the ECFs on this as there is NO unanimous consent on this among them.