Unexpected flex-box behaviour when using non-trivial Visual Element hierarchy

Unity: UI Toolkit Framework

6.3.X

6.2.X

6.1.X

6.0.X

How to reproduce:
1. Open the “IN-107984“ project
2. From the Project window open the "DynamicLayoutExample2.uxml" UI Document
3. Observe

Expected result:

"ContentBox1" VisualElement shrinks when document size is reduced
In "ContentBox2" the "ContentRight" VisualElement does not exceed parent element border
"ContentBox3" VisualElement encapsulates the "ContentRight" VisualElement
In "ContentBox4" the "ContentRight" VisualElement does not exceed parent element border

Actual result:

"ContentBox1" VisualElement does not shrinks when document size is reduced
In "ContentBox2" the "ContentRight" VisualElement exceeds parent element border
"ContentBox3" VisualElement does not encapsulate the "ContentRight" VisualElement
In "ContentBox4" the "ContentRight" VisualElement exceeds parent element border

Reproducible with: 6000.0.0b13, 6000.0.54f1, 6000.1.12f1, 6000.2.0b10, 6000.3.0a2

Reproducible on: macOS 15.5 (M1 Max), Windows 10
Not reproducible on: no other environments tested