Custom control text is not visible when adding it to the UI Document

Reproduction steps:
1. Open the attached project “ReproProject”
2. Open the scene “SampleScene“
3. Observe the result in the Scene or Game View

Actual result: The text cannot be seen
Expected result: The text is visible

Reproducible in: 6000.5.0a5, 6000.5.0a9, 6000.6.0a1
Not reproducible in: 6000.0.71f1, 6000.3.12f1, 6000.4.0f1, 6000.5.0a4

Reproducible on: Windows 11, macOS 26.0 (M1)
Not reproducible on: No other environments tested

Reproducible on devices:

• VLNQA00375 - Galaxy S21 Plus 5G (SM-G996U), CPU: Snapdragon 888, GPU: Adreno 660, OS: 11

Notes:

• Reproduces in Standalone Player as well
• "testcontrol.cs" Custom Control script is attached to a VisualElement within the UIDocument in the scene
• The text is visible in UI Builder when accessing the .uxml file which contains the text (can be accessed by double-clicking on the .uxml file in the Project window)