The governing principle is that a cylinder's force equals pressure times effective piston area, and its speed depends on the volume swept per unit flow, so a symmetrical piston gives symmetrical output.

A double-ended (double-rod) cylinder has a rod projecting from both ends, so an equal rod cross-section is subtracted from the piston face on each side.

Because the effective area is identical in both directions, the same pressure gives the same thrust extending and retracting, and the same flow gives the same blade speed each way.

For a cutter positioning a blade from both sides, this matched force and travel means the blade stops at the same true position whichever way it approaches, the bilateral accuracy required.

A single-ended cylinder has a rod on one side only, so the annulus side has less area than the full-bore side, and force and speed then differ between the two directions.

The idea that this design needs more manual adjustment is false, as the symmetry reduces set-up effort rather than increasing it.

It also does not ease synchronising separate cylinders, nor allow different sizes per side; the benefit comes from one balanced piston.

Hence, the answer is It balances force and movement bilaterally for accuracy.