A nice post, sir.
And yes , I agree with you (and historical fact) about the southern states stressing about their possible sudden reduction in very very cheap labor.
Saying 'it had absolutely nothing' may have been a little....absolute.
There is still value in the statement though - especially for people who know little except what the standard history(channel) says.
Portraying the war as a 'war about slavery' is incorrect, and portraying it as that - simplistically - is simply following the political narrative served up,
at the time.
(in my opinion)