> You're getting a little ahead of yourself.

Nonsense.

> First, ontological assertions need to reflect reality.

You're getting ahead of yourself to imply that somehow physicalism does not reflect reality, or that an assertion has to be proven to reflect reality before being made.

> That is, they need to be true or false

No, that's not what reflecting reality means. Of course ontological assertions are true or false, if they aren't incoherent, but that's neither here nor there.

> and many philosophers, including prominent scientists, don't think they qualify.

What's this "they" that don't qualify? The subject was physicalism, and again almost all scientists and most philosophers of mind subscribe to it ... which leaves room for some not doing so. Whether or not the outliers are "prominent" is irrelevant.

> Indeed, the arguments against ontological realism are more airtight than any particular metaphysical theory.

That's a much stronger claim than that physicalism is wrong ... many dualists are ontological realists. And it's certainly convenient to claim that there are airtight arguments for one's views, and easy to dismiss the claim.