Lifts from the "tall" position specifically target your ability to finish you pull and get yourself under the barbel faster. Catching the barbell lower and quicker will allow you to increase your lifts since you will not be able to pull the barbell as high. By starting in this position, you limit the ability to throw your hips out front, which is a HUGE fault by many lifters. Focus on finishing your pull VERTICALLY instead of bouncing the barbell off the hips/thighs.
To perform, start with the bar at the high thigh / hip region, with majority of your weight in the heels. With you back taunt, arms straight, and chest up, quickly and forcefully extend your ankles, knees, and hips to drive the bar vertical, not out. Finish the movement with a hard vertical shrug, allowing the elbows to follow the shrug to the bar higher, and land in the full catch position.
This is a sink or swim exercise. Many lifters fail to finish their pulls vertically, and in turn bounce the bar off their hips creating horizontal displacement, which in turn will lead to the bar being off track when it reaches the catch position (missing lift out front or too bar behind). This exercise will teach vertical pulling and maximal speed and lockout in the catch.
This exercise can be used in pre-workout routines or as assistance work for 2-5 repetitions with 30-60% of maximum for most lifters.