How to reproduce:
1. Create and open a new project
2. Turn on Internal Mode
3. Make sure that the Inspector window is open
4. Select the "Scenes" folder from the Project window

Expected result: Redraw indicator of the Inspector window flashes once
Actual result: Redraw indicator of the Inspector window continually flashes

Reproducible with: 2021.1.0a1
Not reproducible with: 2018.4.28f1, 2019.4.12f1, 2020.1.9f1, 2020.2.0b7

Notes:
-This seems to be reproducible by selecting any Asset or folder from the Project window or a Layer from the Animator window
-This isn't reproducible by selecting GameObjects from the Hierarchy window, States from the Animator window, Tracks from the Timeline window
-Docking and undocking, locking and unlocking the windows doesn't change the behavior
-Normal and Debug modes don't affect the behavior also