Ken was making controlled shots not high powered drives in that video. Resting is good to diagnose if your form variances come from being tired or not managing slower speed throws well. An example of possible problems with sideways accuracy in slowed down form is that if you don't push hard with the left leg and having lost much momentum you may not turn toward the target with the body and the disc leaves left. Momentum changes between forms, keeping the knees bent enough to push hard from and being in good enough shape to really push enough to be able to aim at the target without compromising form, timing power generation and positions is a matter of coordinating all moving parts at different speeds. You need those eventually to control distance and when discs stop pushing through initial hyzer/anny and start to move to the side like the angle would suggest.
Flat shots need running on the center line of the tee and planting each step on the center line. Anhyzer needs running from rear right to front left with the plant step hitting the ground to the left of the line you're running on. Hyzer is the mirror of that.