A real attribute is not treated as merely a relation constructed by comparing two things, as knowledge and power are regarded as real attributes. A relational consideration essentially depends on comparing relata, as with being to the right or left of something.
An Ashʿarī formulation interprets takwīn through the relation of power, will or the fact of creation. The Māturīdī account holds takwīn to be a real eternal attribute, while its relations and effects vary with creatures.
Simply calling something “eternal” does not establish whether it is an independent real attribute or a relational description. Those are separate issues.