I intended to say the opposite, i.e., for all T (not equal to P or not-P), P is independent, but perhaps that is wrong too.

The quantification over T is still kind of weird, though. In a formulation like `for all T, (T and P consistent and T and neg P consistent)` is trivially false, just take `T = {neg P}` and now `{P, neg P}` is inconsistent.

We're never trying to show P is independent of all theories, just some specific one.