I think, the effect here is similar to a situation where you take 2 balls of different weights, for example a 🎾 and a 🏀, stack them with the smaller ball on top and drop them. If you drop them both from, say, 1m height, when bouncing off ground, the 🎾 will bounce up much higher than the initial 1m. Because the heavier ball will impart some amount of its kinetic energy to the smaller ball.