The point, I think, is that, while the whole looks like a compound sentence, in which the truth of
one component may affect tht truth of the whole, here there is no whole in that sense. That is,
the two claims are independent and their combination does not make a new entity (more than any two
successive sentences) whoses truth is somehow related to the "parts." So a contrast with various
attitudinals and logical connectives and what not. This is merely cutting off any implication of
similarity to some of the other things around in this area of the grammar. I think.