Interesting that the SpaceX rockets have the same behaviour when landing. I read somewhere that was because they have no throttle control and are on/off, but I'm no authority.
Given the constraints, it's surprising they don't lose more rockets during the landing phase.
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.