In this case you are simply interpreting the original Newcomb to mean something absurd, because causality cannot "genuinely flow in reverse" in any circumstances whatsoever. Rather in the original Newcomb, Omega looks at your disposition, one that exists at the very beginning. If he sees that you are disposed to one-box, he puts the million. This is just the same as someone looking at the source code of an AI and seeing whether it will one-box, or someone looking for the one-boxing gene.

Then, when you make the choice, in the original Newcomb you choose to one-box. Causality flows in only one direction, from your original disposition, which you cannot change since it is in the past, to your choice. This causality is entirely the same as in the genetic Newcomb. Causality never goes any direction except past to future.