The slower you get an airplane, the higher the angle of attack to hold altitude or sustain a given descent rate, the higher the angle of attack, the more drag. At a certain point if you get slow enough it requires an enormous amount of power to recover or even just to sustain altitude or keep a desired descent rate. It has nothing to do with spool times, it is simply drag vs. airspeed. You can even demo this in a 172. You get a 172 slow enough, you'll need full power to hold altitude. Each airspeed has an associated amount of thrust to maintain altitude, at some point down low towards the stall..the amount of power starts going up like crazy just to hold altitude, and in theory at zero airspeed would have the nose pointed at the sky to hold altitude. When you run out of enough excess power to initiate a go-around you are now below the power curve required to avoid hitting the ground, or arresting the descent.