Reproduction steps:
1. Open the user's attached project and Scenes/SampleScene scene
2. Enter the Play mode
3. Click on the Hierarchy window (or lose focus from the Game view in any other way)
4. In the Game view, click on the square (do not let go of a mouse button after pressing)
5. Observe the Console window

Expected result: OnPointerDown() is called
Actual result: OnPointerDown() and OnPointerUp() are called on the same frame

Reproducible with: 2020.2.0a12, 2020.2.3f1, 2021.1.0b4, 2021.2.0a4
Not reproducible with: 2019.4.19f1, 2020.2.0a11
Could not test with: 2018.4.31f1 (events did not get triggered)