Off hand is normally the work of the walking around woods hunter and at normal wood distances getting down on one knee will most often do little to improve your view of the animal. Taking it to the extreme, go down flat on the ground and have a look at what you can see and what pops up in front of you.
Grab on to something if you can, go down on one knee if you have time, practice for those times when you can not.
Nor does going down on a knee grant any favors for when the animal is moving. If it did, then skeet would be shot on one knee.
Addition: Shooting only from the bench does nothing for learning how to correctly mount a rifle quickly. Like many things there is a wrong and right way. It does nothing for learning how to subconsciously have the feet set themselves to the best advantage. There is more to hitting things than pulling the trigger.
Last edited by battue; 06/06/16.
