The bounciness combine value of a physics material affects the colliding objects

Steps to reproduce:
1. Open attached project.
2. Press play.
3. Observe how all the objects keep bouncing although they have physics materials that have bounciness values different than 1 and "Maximum"
4. Change the Combine parameter of the plane material.
5. Observe how the objects' behaviour changes accordingly.

Expected behaviour: According to documentation, "When two bodies are in contact, bounciness and friction modes are applied individually to each agent. So, when body A has a friction combine mode of Average and body B has mode Multiply, then A is going to behave according to average parameters and B according to multiplied parameters". According to the above, the Bounce combine parameter of an object should not affect the objects that are colliding with it. Only the bounciness value should affect them.

Actual Result: The colliding objects with the plane are affected by the combine value of the plane

Reproduced with: 5.4.5p3, 5.4.0f3, 5.5.4p1, 5.5.3p4, 5.5.0f2, 5.6.1p4, 2017.1.0b10, 2017.2.0a4,