Progress bar does not appear when closing one of multiple running Unity Editors

Reproduction steps:
1. Open the attached project "ReproProj"
2. Open another Unity project to run multiple Unity Editors
3. Close the second Unity Editor
4. Open the progress bar in the first Editor from the menu bar using “Command > Show Progress Bar"

Expected results: The progress bar appears
Actual results: The progress bar does not appear

Reproducible with: 6000.3.2f1, 6000.4.0a5, 6000.5.0a3
Not reproducible with: 6000.0.64f1

Testing environment: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested