Collapse from one column at page s ≥ 1 or one row at page s ≥ 2

In homological indexing, zero terms on page $s$ remain zero on every later page by the subquotient clause in [F2]. Thus if all nonzero terms on page $s$ have first coordinate $c$, the same holds on every page $r\ge s$. The $r$-differential changes the first coordinate by $-r$. Since $r\ge s\ge 1$, every differential has at least one zero endpoint. All are zero, giving collapse by [F1].

For a single homological row, the second coordinate changes by $r-1$, which is nonzero when $r\ge s\ge 2$; persistence from [F2] and the same endpoint argument give collapse. By [F3], cohomological pages likewise retain the one-row or one-column support after reversing both coordinates, while their changes are $r$ and $1-r$, again nonzero under the respective bounds. The bounds matter: $d^0$ may run inside one column, and $d^1$ inside one row; those maps are not forced to vanish by the stated support condition alone.