Meaning
The relative seam defect is the ordinary gluing jump restricted to boundary data that already satisfy the source-twisted matching law.
After incision, there are two legitimate boundary conditions:
The source-twisted boundary space is
On that space, the relative seam defect is
This is the small distinction that makes the analytic argument honest. The central lift satisfies the source law, so its source-twisted jump vanishes. The energy detector therefore cannot be that same jump. The relevant defect is its failure to satisfy the ordinary, source-free admissible gluing law.
Example (illustrative)
If
The source condition is satisfied exactly, while the ordinary seam still sees a nonzero mismatch.
Scope and limits
The defect is not yet an energy. It becomes an energetic statement only after the Dirichlet restriction bridge evaluates it with the boundary form inherited from the collar Hamiltonian.
Source
Phenomenological Implications I, §§5.1–5.3, especially Proposition 5.1, Definition 5.2, and Remark 5.3.