Happytrails,
It is no problem connecting or disconnecting the fiver. Most hitches are set up to lock automatically when you back into the king pin. Then you just verify it is locked and secure the lever.
To disconnect, pulling the lever to unlock the hitch is made easy by unloading the hitch before you pull it.
If when you try to pull the handle it is tight, just release the truck out of park and allow the tension to relax, if on unlevel ground, you may need to put in fwd or rev then park and set brake to hold the truck in the "sweet spot" then pulling the lever is easy.
The fellow you saw, must not have done that, and just gave it a yank. Which is ok too as long as your king kong!
Cheers,
Bill