Kind of interesting.. I would like to point out this seems to be specific for the US.
But also.. In that case, when I commission an artist to paint my portrait, surely I can't claim to be the artist.. But I'm no lawyer.
I'm not sure there is a contractual agreement in GitHub's co-pilot that says: "Any code you write here is commissioned work". But honestly I didn't read the T&C's.
So I think you MAY have debunked my analogy, but not the main reason for the analogy.