They 'rev up' due to their fairly low Radius of Gyration (2.52 for both). You actually release them with a higher RPM than a ball with a higher RG rating. If your average RPM's are about 300, you would release it with about 10 more RPM's than a ball with a 2.62 RG rating. I nerdily stumbled upon an equation on the internet that I used to compute this.