It also offers more in the dynamic between Conner and Jon, I think.
I disliked the "half Lex" retcon, and I still prefer the original where Conner was a clone of Westfield with some hefty geneic engineering to mimic Superman's powers. But as far as basic, foundation-level story building goes? "Superboy; clone of Superman and Luthor" is a stronger hook than "Superboy; clone of random science guy."
It has less nuance, it's more basic bitch, and it makes the mythos a little smaller, but it's an easier sell. And it's got what, almost twenty years of precedence behind it now? I think at this point Conner has been a Clark/Lex clone longer than he was a Westfield one. I don't see this changing, ever, for good or ill.