Sure, plenty of readers of Matthew 22 in Hebraic Hellene have troubled over how the Shema is rendered in its presumably goyish Greek (perhaps the work of a gentile writer and/or his gentile Christian editors). But I think Matthew is up to something here. Through the long arc of confronting hierarchies of social constructs, he's played on the word κύριος.
Might this gospel be at times a confrontation of the Roman κύριος himself? The Empire claims he is the son of God.
And so when Jesus replies to fellow Jews all together concerned with him over what the Hebrew scriptures claim about God, about humans, and about him, why not refer to him, as the LXX translators do, all Jews, with κύριος?
And when quoting David referring to the Messiah (whom in Greek will be translated by Christ, or literally the One Bathed in Oil as Odysseus was), why wouldn't Matthew have Jesus use the same phrase κύριος.
And why not ask a salient, rhetorical question like this one that upsets all notions of who can call whom Kyrios and what that means?
εἰ οὖν Δαυὶδ καλεῖ αὐτὸν κύριον, πῶς υἱὸς αὐτοῦ ἐστιν;