Wondering if 11venthhour is more interested in PL'ing (using max weight & the bar held low on the shoulders/traps), rather than BB'ing (mid range weight with bar resting higher up on the traps/shoulders). Because that clip is a teaching method for heavy squatter's, with focus on PL/Olympic lifters. BB'ers do not always need excessive weight during squat/leg workouts to gain impressive muscle mass.
In any event, have to get real and understand their are some who are not gifted at heavy squatting no matter how hard they try. Even with all the tips and advise they may gather over the years (same thing for the DL & bench for that matter.....those 400 benches people talk a lot about are not all that doable for most folks.). Can always improve the lift greatly by insuring all the links involved in the squat (from the neck all the way down to the foot stance and even toe gripping) are trained to the max and are all firing off for full potential of force. But if the individuals body/leverage mechanics are just not set up for moving huge weight, than that will be very limiting. Bad news is more injury, than benefit, may develop.
There are a few methods that I, and others, have used for greater squat/leg power. Might try wearing raised heels lifting shoes/boots or squat with the heels on a 2X4 or a pair of 45 plates. Sets a better balance and also hits the lower quads quite well. For a lot of guy's the lower back can feel less stress and fall in line with the rest of the body when squatting this way. Actually, if feeling undo stress in the lower back, when squatting, your form/style is wrong for your body type.
One legged step-up's (not to be confused with one legged squats) on a box or bench, with the height around your knee level. Always a good idea to work one leg at a time to insure equal strength levels and the all important balance. This also affects the hams/glutes/hips quite well. Try using a BB (some prefer a pair of DB's). adding weight as you get stronger.
Sissy squats, an excellent quad stretcher, which track and football players use a form of in training. This exercise must be learned the correct way. Suggest Vince Gironda method. You will know if your doing it right by the outstanding stretch and unreal burn. Good Luck.