Correct, the Bowden cable is also called the control pressure cable, its function is to counter act, balance other pressures in the valve body, which are used to move valves that controls a particular shift. By removing that counter balancing force, the shift valves are free to move with no opposing force that controls shift timing.

The problem can still be the kick down solenoid, a stuck valve in the valve body, a leak in the B2 piston and K2 drum can cause no 4th Gear.

This is an easy test to eliminate control pressure as the cause for a late and no 4th shift.