[Galxeagle]

The key reason is that an extra second of time spent hovering or close it is another second of resisting gravity, which takes fuel, so the most efficient hypothetical ‘burn’ is one big bang ‘hoverslam’ right at the end and 0 seconds spent fighting gravity

The SpaceX Falcon 9 rocket does have throttle control, but at minimum thrust the thrust-to-weight ratio is still greater than 1, which means they have to hit 0m/s at exactly 0 feet of altitude or they start going up again. I’d imagine they time their ‘hoverslam’ to take 2x minimum thrust (or some other multiplier) and then adjust up or down through the manoeuvre.