Anyway, for the lower back, execution ends as follows, "Return and repeat." For the glutes, you have, "Return by bending knees forward slightly while allowing hips to bend back behind, keeping back straight and knees pointed same direction as feet. Repeat." As stated earlier, a *slight* difference.
That's like the difference between saying "drive from your house to the office" or saying "drive to your office by backing out of the driveway, going east on 7th street, and then north on Bucky Avenue."
Doesn't sound like much, but for the barbell squat, a difference in the preparation wording affects the target muscle group (quads vs glutes). I don't know if the difference in the deadlift execution is significant or should be ignored.
Well, it should probably be ignored by most of us. The general idea is that by "sitting back" more, keeping the shins more vertical you hit the glutes more. May not hit the quads much less, and the difference seems slight to me. I worked for a long time to try to achieve vertical shins, and finally realized that this is a powerlifting influence that I didn't really need, and I actually did better if I allowed my knees a little more freedom to move forward. This is affected by the width of the stance as well. With a wider stance, you keep your shins more vertical and vice versa. I still try to move the hips back before the knees start bending, and try to reach back with my butt, but if my patellae pass the vertical line that starts at my big toe, I'm not going to lose sleep over it.
The important things in squat are a neutral spine, knees staying aligned (in the same plane as) the feet, and getting at least to parallel. If you do those 3 things, it's a safe and useful exercise. Everything else is just flavor variation. Like Kenny C says, you have chocolate and you have vanilla, but it's all ice cream.