Button hover state uses default theme color when a custom .uss is applied

Reproduction steps:
1. Open the attached "repro_IN-100398" project
2. Open the "Assets/Scenes/SampleScene.unity" Scene
3. Enter the Play Mode
4. In the Game view, hover over the "Button", which is located at the top
5. Observe the color of the button

Expected result: Color of the button changes to blue
Actual result: Color of the button changes to gray

Reproducible with: 2023.2.0a13, 6000.0.48f1, 6000.1.1f1, 6000.2.0a10
Not reproducible with: 2022.3.61f1, 2023.2.0a12

Reproducible on: Windows 10 (22H2)
Not reproducible on: No other environments tested

Notes:

• Reproducible in Player
• Related Discussions thread: https://discussions.unity.com/t/pseudo-classes-dont-apply-when-used-with-theme/1636596