Re: Spey cast....
We use some one-handed spey techniques for adaptive casting work, and...frankly...I use them for some really tough casting scenarios, myself. And the only diff is how you're holding the rod. The casts are the same.
I agree with Cliff. Except I would say that the double spey is what I have found to be the one I actually use 90% of the time when a spey technique is beneficial/necessary.
I can see how in two-handed spey the snap-t has a real-life usefulness. But the snake roll is for show, not go. It's just another way to do the same things...style over substance. So I wouldn't even worry about it. And I'd also view with a certain amount of conservativism (polite for cynicism) the instruction I was getting from my buddy. Perhaps he's a bit more interested in showing off than in subtance and results? Just an indicator that would make me question, not saying it's true. I have no idea!
But I do see this quite a bit: somebody teaching someone to cast who really steps all over the real goal of teaching someone to be an effective caster so they can have more fun fishing because they're too busy having more fun proving what a great caster THEY are...at least in their minds. I have a saying I picked up from one of my best college professors about that:
"There is no such thing as a great teacher with an ego problem."
Enjoy yourself! Spey techniques can really make you a much more versatile caster...being able to brave winds and currents that casters unequipped with spey techniques just can't cast in, and being able to effect long casts and mends without backcast room. But I will say this: if you don't have a medical condition fatigue is...as you properly identified...a definitive indicator of improper fundamental technique! And with a big ole spey rod, heavy line way on out there, etc. you can actually hurt yourself pretty quickly doing it the wrong way repeatedly. Pay attention to your body. It'll tell you when you're messing up. A good fly cast is one of the lowest impact activities you can engage in. It shouldn't hurt or wear you out. Fly rods are tremendously powerful lever/spring tools. They require very little physiological kinetic energy applied to do amazing amounts of work. But they have to be used properly. This is even more true of a spey rig than a typical one-handed rod/reel/line.