TWT: Correct. That is why I suggest that people "NEW" to doing GM'ing or SLDL's preform them with a straight back more as a learning exercise. Once you advance to 300-400+ than you have not much of a choice (mechanics, gravity, etc) and all that, than to round the back (depending on bwt at times) . And yes, this can be applied to the wide to extra wide stance that most PL'ers do when approaching extreme weight. That is where the hamstrings come in strongly. The ROM is not near a 90 degree angle. Though, as you suggest, at times a squat can resemble more of a combo GM'ing and squat. But as long as you get green lights, who really cares..
Any exercise that can mock or mimic squats, Dl's or what ever have a solid place in any workout. It is all about strengthening the chain of muscles involved in any exercise. Just like chains, bands, board presses, PR, etc for benching is part of training. But a basic foundation in lifting should be put under anyone's belts before going into these more advance and serious training methods. Give it 9 months to a year to adjust (even for BB'ers) and ready the body for extreme heavy training. And than approach every workout with serious intent. The Black flag is raised.
Two of my favorite exercises are GM'ings and SLDL. Both have paid off very, very well over the years. Lower back, hips, hams and the whole link of muscles from the feet all the way up to the traps and neck muscles. No matter if it was football or lifting, those two exercises did outstandingly well for me. I believed they even helped me a great deal, and I paid more attention to both of them, after major lower spine/back surgery from being blinded sides in my last college football game. Bowl game by the way. Good Luck.
