I figured I get a question on that. When musky fishing you're sight fishing structure or fishy looking places IE a downed tree in the water, a rock or over hanging branches along a cut bank ( I fish rivers more than lakes) slack water where they lurk waiting for prey to come by.Right Hand ?? Looks like according to the photo with Left hand retrieve, and assuming your Right Handed . . . this would be the correct or shall I say more convenient way to retrieve line and not having to switch hands constantly on the rod as I've seen so many "struggle with" ! Being the way your set up I would think it would be your LEFT hand putting pressure on the spool for "drag effect" ! That's the way I do it when I run into a BIG Runner so as to not have to "mess with" the drag knob - very awkward, as you must know . Why Lines and Big Fish !
So when casting you have quite a bit of line stripped from the reel at your feet or in a basket. Casting distance is constantly varying so usually more line out.
Muskies tend to hit at two places, either right when the fly hits the water and the first few feet or pretty close to the boat. When a musky eats it you need to strip set and then keep the pressure on so your right hand is pinching the line as you re-grab the line with your left hand and play the fish and take in more line. You really don't have much chance of reeling the stripped line unless the fish takes a big run and takes all the stripped line with it. So you really are using both your right and left hands as your drag. Most fish are boated with out ever using the reel to take line in. rarely do you get to the point of relying on the reel's drag or your left hand palming the reel to add drag.
It's much easier to keep the pressure on stripping the line by hand than using the reel especially during a lot of head shaking. Keep in mind any experienced musky fly-fisher either pinches the hook barb off or files it off.
Does that make sense now?