The tooltip does not appear when hovering the button in Modal Window on Windows Editor

Unity: IMGUI Framework

2022.2.X

2022.1.X

2021.2.X

2023.1.X

2020.3.X

Reproduction steps:
1. Open the attached 'ToolTipsNotWorkingOnModalWindows' project
2. Go to the 'Bug -> Open modal'
3. Hover the 'Hover me' button

Expected result: The 'This is an awesome tooltip' shows up
Actual result: No tooltip is displayed

Reproducible with: 2020.3.30f1, 2021.2.19f1, 2022.1.0b16, 2022.2.0a10
Could not test with: 2019.4.36f1 (the tooltip appears all black)