When your just a bystander, you can’t really complain if someone else’s dyno testing doesn’t follow the priorities you’d have if it was your test.
That being said, “if it were me”……. And I was going to orchestrate a SBM head shootout test……..I’d want to use a short block and induction/exhaust system that would make it so the heads are the HP limitation.
Big enough cam, maybe a ported manifold, good sized carb and headers…….parts you’d expect to be capable of producing in the area of 600hp.
Then, see how much of a limitation each head presents to the combo.