The manual calls out getting off the seat, then engage the PTO, which is how it's done on my old 4400 too.
I'm not sure why one would have to stay on the seat for two or three seconds....is the manual in error?
Using Rear PTO (Operator off Seat)
NOTE: The rear PTO can be engaged with the operator off the seat. The Safety Interlock System will stop the engine and all implements if the mid-PTO is engaged and the operator gets off the seat.
Engaging Rear PTO
1. Sit on operator痴 seat.
2. Move transmission to neutral position:
PowrReverser: Depress clutch pedal completely and move the transmission gear and range shift levers to the N (neutral) position. Move the reverser lever to the N (neutral) position.
eHydro: Move the range shift lever to the N (neutral) position.
3. Lock park brake.
4. Push all PTO engagement knobs to the disengaged/off position.
NOTE: The starter will not crank if the rear PTO knob is pulled to the engaged/on position.
5. Start the engine and adjust speed to 1500 rpm.
6. Get off the operator痴 seat.
7. Engage rear PTO:
Tractors without cab - Pull the rear PTO engagement knob to the engaged/on position.
Tractors with cab - Move the PTO selector lever to rearward position for rear PTO only. Pull the rear PTO engagement knob to the engaged/on position.
8. The instrument panel PTO engaged light will illuminate when the rear PTO is engaged.
9. The engine should continue to run.
10. Adjust the hand throttle lever forward to the desired speed for implement used.