Beyond a certain density, the wrist can't keep up. Sixteenth notes at ♩=120 are 8 strokes per second per hand — if you tried to power each one with the wrist you'd cramp inside thirty seconds. The hand's other engine is the rear three fingers — middle, ring, and pinky — which curl and uncurl behind the stick to flick it into the head while the wrist is parked.
Where the wrist is for power and accents (loud), the fingers are for speed and ghosts (soft). They're complementary, not interchangeable. Brian Blade's edge-of-snare ghost notes — the ones underneath everything he plays — are pure finger control: the wrist barely moves, and the fingers tap the stick into the head with millimetres of motion.
Grip foundation. The fulcrum is the thumb-and-index pinch. The rear three fingers are behind the stick, curled around it but not gripping it. As the stick rebounds, those fingers catch and re-throw it.
The motion. Pinky/ring/middle extend: the stick rotates on the fulcrum and the tip drops to the head. They contract: the stick rebounds and resets. The wrist stays still through both halves. The whole motion lives in about one inch of stick travel.
The transition. When you need to add a loud note (a backbeat, an accent), the wrist re-enters and lifts the stick to full height. The fingers go quiet for that note. Then, immediately after, the wrist parks and the fingers take over again. This handing-off between the two engines is the entire skill.
Once it's installed, you'll discover what the fingers actually do for music: they make ghost notes possible at any tempo, they make buzz rolls smooth, and they let you play 32nd-note runs on the snare without sounding tense. They're the engine of soft and fast.