You obviously didn't read the comment you're replying to. No one is challenging that.
Having the same TEAM in charge of the OS and in-house hardware is an entirely different story.
It's a conflict of interest because the person Samsung is talking to to have a feature implemented into the OS baseline may be the same person in charge of defining the competitive featureset for the next Google hardware.
Now this person knows that the product he and his team is designing will compete with a yet-to-be-announced Samsung-product with a new feature.
So his interest to support a licensee being successful with his product is in conflict with his interest to create a more successful competing product.
And even if he isn't, for SAMSUNG just the potential of this situation to happen can be enough to NOT cooperate with this team and scale back communications with the Android team as a whole.