A shared predicate does not establish equality in every perfection. Two people may both rightly be called knowledgeable or courageous, though their accomplishments and capacities differ.
Similarly, the existence of foundational faith in two persons does not erase differences in detailed knowledge, good works, reverence, and perseverance. These may explain differences in merit and reward.
This is an illustration of a conceptual distinction, not a claim that every feature of a human trait can be transferred without qualification to faith. Possessing a description, its quality, and its perfection must be carefully distinguished.