Point being, it's OK for the feet to leave the floor. If they do, you are "jumping" though that is not necessarily the intent, rather it is the natural result of an explosive finish to the pull.
I know some advocate that the feet never leave the platform.
At some point, the barbell is no longer elevating and any arm action at that time is essentially pulling the lifter under the bar. As the force imparted on the bar is not raising it, relative to the ground, as the bar is returning to the platform, the position of the feet is irrelevant.
It is relevant and critical that when the bar is caught overhead or shouldered, the feet are in a stable receiving position which allows for balance and recovery.
I would encourage lifters to extend fully, with enough force that the feet leave the platform. I would discourage a conscious flexion of the legs to accomplish this. The feet leave the platform due to the force of the finish pull. The legs flex to get into the receiving squat position.
Hope this makes sense.