Override indicator (It's a blue line which comes next to the edited property and the property name being bold) doesn't appear on changing prefab instance rigidbody's constraint property

Steps to Repro:
1. Open attached project
2. Select cube in the 'Sample Scene'
3. Change the 'Rigidbody Constraint' property

or

1. Hierarchy window > right click
2. 3D Object > Cube
3. Select cube > Add component
4. Add a Rigidbody to it
5. Drag the cube in the project window to create its prefab
6. Change the constraints property

Actual Result:
1. On changing any of the constraints, override indicator doesn't appear
2. Constraints overrides can be seen through override drop down

Expected Result:
1. Override indicator should appear next to constraint drop down and next to the edited rotation or position property
2. Edited property name should turn bold

Occurring with:
Version 2018.3.0a2 (e9113db2e9bf)
Thu, 14 Jun 2018 21:56:37 GMT
Branch: prefabs/improved

Environment:
Windows & Mac