The reason for the speeding up roll is based on the way physx generates contact points. There are two approaches and they both have advantages. The current default behaviour is designed to get stable stacking of boxes and objects, but comes with inaccurate contact points. The new option, which can be turned on in the project settings as of 4.8, generates accurate contact points but with reduced stability of stacked objects.
In the case of spheres rolling, inaccurate contact points cause the simulation to gain energy which causes artifacts.
The game specific part is that you need to decide which feature is more important for your project.