In a clean or snatch the proper hip position will depend on your body type.
First you have to understand the key things of the starting position:
1. The shoulders should be above or slightly in front of the bar
2. The knees should not be in front of the elbows
3. The hips should be as low as possible while respecting 1 and 2
Because of these conditions someone with longer legs OR a longer femur relative to his tibia will have a higher hip position than someone with shorter limbs or a longer tibia relative to his femur.
Now, why do we want a lower hip position compared to a powerlifting/strength deadlift?
Because in a deadlift the lift pretty much ends when the bar reaches the upper thigh/hip crease. In the Olympic lifts IT STARTS THERE.
What I mean by that last point is that in the Olympic lifts you don't explode straight for the floor... you aren't yanking the barbell from the floor. The explosion occurs somewhere between the mid/upper portion of the thigh in the clean and between the upper quad and hip crease in the snatch.
Since you have to explode when the barbell is high you need to have legs that are still somewhat bent to be able to explosively drive the barbell up.
In a strength/powerlifting deadlift the legs are pretty much straight or even lockout out when you reach the upper portion of the thigh or hip crease.
In you are in that position in the clean or snatch you can't use your legs to explode upward. All you have left is your lower back and arms which makes the lift turn into am ugly looking cheated reverse curl or something like that.
In a powerlifting deadlift it's fine to use a higher hip position at the start since it gives you are strong leverage off of the floor. But in Olympic lifting you don't need that: the role of the first pull in the OL (from floor to above knees) is simply to get the bar in the right position to accelerate with the legs in the later part of the lift and the weights used do not require an advantageous lever from the floor like in a strength deadlift.
For that reason someone focusing on the Olympic lifts should use deadlifts mimicking their Olympic lifts starting position (lower hips), not a powerlifting deadlift (higher hips): to strengthen the body positions involved in their lifts.