Selected value doesn't reflect in dropdown for "Compute positions" and "Adjust Time scale" in blend tree . Refer the attached video

Steps to reproduce:
1) Create a new project
2) In Hierarchy, Right Click > 3d object > Cube
3) Window > Animation
4) Create an animation for cube
5) Create a blend tree for a state with that animator parameter
6) Select the blend tree > Change dropdown values for Compute positions and Adjust time scale

Actual result: Selected value doesn't reflect in dropdown for "Compute positions" and "Adjust Time scale" in blend tree . The dropdown value always shows "Select"

Expected result: Dropdown value shows the selected value for "Compute positions" and "Adjust Time scale" in blend tree

Occurring on: 2020.1.0a14, 2019.3.0b12, 2019.2.0f1, 2018.4.12f1, 2017.4.34f1

Environment: Both Windows and Mac