QM3 asks whether the relational configuration space naturally separates into more than one invariant sector.
What QM3 defines provisionally
A sector is defined provisionally as a region left exactly invariant by transport. A single such sector behaves consistently, and nothing in the framework rules out more than one.
What remains unknown
Whether an invariant sector structure exists at all in the realised configuration structure. QM3 does not derive the existence of sectors from the primitive PDT foundations.
Why this matters
Without several sectors, there is nothing to couple.