The lifters who split jerk prematurely tend to do so at the apex of the dip back up, specifically at this point:
Take note of how his feet are almost off the ground. Many lifters choose to jerk the bar during this ascent. As a result the front foot leaves higher off the ground. Their foot does a sort of hop forward.
I've learned from other sports that footwork has a standard rule - when the feet move they should move while staying as close as possible to the ground. My short experience with kendo, eskrima, grappling, and ballroom dancing hold this fact true. There are no hops or tall strides.
Allowing the foot to rise higher than needed creates more distance it has to travel. Not only that but imagine where your foot would be more stable. When you have a heavy bar overhead, do you want your foot near the floor or far from it?
The weightlifting coach at my school gave a great tip. He said "slide" your feet out instead of jumping them out. It's a good way to visualize how to split as you drop under the bar - not while you're still driving the bar upwards.
It takes patience to not split early but if you wait you'll have a more solid jerk in the end.