As I've suggested, that "nothing but" judgment isn't itself part of game theory. You're applying a larger philosophical perspective here.

Is that like Archimedes' "a place to stand" not being "part" of his lever? I don't see what difference it makes to my claim or yours.

Moreover, it's clear to me that what may originate as a mere workaround can take on a life of its own, generating a new game the outcome of which is determined by higher-order rules.

Some dogs are black. Fido is a dog. Therefore, Fido MAY (or may not) be black.

In the case of emergent morality, you would need to show that those rules are either irrelevant or empty or that they reduce to prudential game theory.

We've been over that. I don't have to prove ANYTHING to YOUR satisfaction. Readers can decide who needs to prove what to THEM. I'm happy with the arguments lying where they lie.

So are the philosophical and religious discourses of morality either nonsensical or just roundabout ways of talking about the more fundamental, game theoretic issues?

The latter.

Supporting an affirmative answer would be a tall order.

I'm not sure what an "affirmative" answer to a "pick one" question is, but I don't see how your assessment of the difficulty of making my case bears on its truth.