A metric form is not a cubic scalar observable

Model 3 represents matrix elements of a prescribed sourced response and certain regulated curvature smearings. It therefore establishes a restricted, form-level quantization of that response. It does not establish an unregulated self-adjoint metric field, a canonical metric algebra, or a quantization of

The latter is cubic even at the classical level. Its ordering, distributional kernels, and domain estimates are separate tasks.