Dual-Aspect Monism as defined in this wiki is the claim that physics and consciousness are two aspects of the same underlying phenomenon. As such, their relationship is like that between the edges and faces of a cube, or between two shadows cast by a cylinder from different angles. Crucially, this relationship is a logical consequence of the structure of the universe, rather than a fact governed by an explicit set of laws.

you're right - there is a way to interpret functionalism that makes it look very similar to dual aspect theory. if we say the functional/relational patterns themselves constitute the "mental aspect" while the physical substrate constitutes the "physical aspect," they start to converge. the key difference is probably in how they frame causality and ontological priority: traditional functionalism still tends to be reductionist - saying consciousness is nothing over and above functional relationships implemented in physical systems. the mental is ultimately explained by physical processes arranged in certain ways. dual aspect theory says both aspects are fundamental and irreducible - neither can be fully reduced to the other. consciousness isn't just what functional relationships "do"; it's an intrinsic aspect of reality expressing itself through those relationships.