Because you can see it in the parts diagram that I pulled up. Single shaft leading to clutch.How do you know that?
Dual clutch requires a inner and a outer shaft, no such thing on any of the Hydraulic Shuttle diagram.
The purpose of a dual clutch is to not slow down the PTO while shifting gears. Mechanical Shuttle or GST requires clutch in. Hydraulic shuttle does not require clutch in for this as it has its own set of clutches.