Reproduction steps:
1. Open the “BugRepro” project
2. Open the “Assets/Scenes/MainMenu” Scene
3. Open the “Assets/UI/UXML (UI Builder)/MainMenu” Visual Tree Asset using UI Builder window
4. In the UI Builder window, observe the “#PlayBtn” Button text
5. Open the Game View window
6. Observe the same Button in the Game View

Expected result: The Button text is rendered in both the UI Builder window and Game View
Actual result: The text is only rendered in UI Builder window and no text is rendered in Game View

Reproducible with: 6000.0.4f1
Couldn't test with: 2021.3.38f1, 2022.3.30f1 (Advanced Text Generator was added in Unity 6)

Reproducible on: Windows 10, Windows 11
Not reproducible on: No other environment tested