If you're passing people it means you're starting behind them. Coasting, you'll accelerate when they've already topped out because you're drafting them. If you pass them relatively quickly then they won't get a return draft so you'll nose out in front of them.
The fact that you end up hanging out 25 meters in front means you're not getting away from them, just passing them and then slowing (due to lack of draft) back to about the same speed.
If you passed them and kept accelerating without pedaling and you would end up out of sight, that's a different story.
When people ask how I descend better, I like saying "I'm dense". It certainly beats explaining to them that coasting on the drops, one leg down, head up, and various other aerodynamic negatives doesn't help them go fast. I'm descending in a chin-to-tire tuck, hands together, elbows and knees in, feet parallel, and I accelerate before I tuck instead of letting gravity accelerate me ever so slowly.
cdr