How to reproduce:
1. Open the user's attached project "NewFeaturesTest.zip"
2. Open the "testScene" Scene
3. In the Hierarchy window select "GameObject"
4. In its Inspector window press the "Thing (A)" or "Other (B)" button
5. Expand the newly created "T" foldout

Expected result: The foldout has an int item inside
Actual result: The foldout has no item inside

Reproducible with: 2022.1.0a10, 2022.1.0b2
Could not test with: 2019.4.34f1, 2020.3.25f1, 2021.2.7f1, 2022.1.0a9 (no foldout is created)

Notes:
- Pressing the other button in "GameObject" Inspector window creates a foldout with an item inside. Pressing the first selected button again will update the foldout item
- Similar to case https://issuetracker.unity3d.com/product/unity/issues/guid/1216937/