What does this equation mean?

Lay all of it out in one table, rows for experiments and columns for the five components, and four columns get real entries: $\eta_{cl}$ constrained at the 10^{-15} level by MICROSCOPE, $\hat\eta_{diag}$ constrained by every dual-species and clock test in the list, $\hat\eta_{coh}$ constrained at the low- 10^{-9} level by Rosi and colleagues’ internal-superposition test, $\hat\eta_{sup}$ constrained by Overstreet and colleagues’ gravitational Aharonov-Bohm result. The fifth column, $\hat\eta_{ent}$ , has nothing in it — not a weak bound, not a preliminary number, nothing. The paper’s proposition on this point is not merely that the entangled component happens to be unmeasured; it proves, within its operator model, that any experiment performed on separable states of two species — meaning any product of single-system states, internal superpositions included — produces outcome statistics that are provably independent of $\hat\eta_{ent}$ , because that operator only ever enters through the joint phase of a genuinely nonproduct state. Run every experiment in the table again, in every combination anyone has thought to try, and the entangled column still comes back empty, not from a lack of effort but because separable-state statistics cannot see it by construction.