How to reproduce:
1. Open project "UIToolkit Bug.zip"
2. In the Hierarchy window select "Open Sprite Shape"
3. In the Inspector window press the "Edit Spline" button
4. In the Scene window select on corners and check Corner setting in Hierarchy
5. In the Scene window select all three corners
6. In the Inspector window press the Corner setting button "Stretched"
7. Select "Stretched"
8. Observe every point's Corner setting

Expected result: All corners Corner setting is "Stretched"
Actual result: All corners Corner setting is not changed

Reproducible with: 6.0.2 (2021.1.25f1), 7.0.2 (2021.2.0b17, 2022.1.0a13)
Not reproducible with: 3.0.17 (2019.4.31f1), 5.1.5 (2020.3.20f1), 6.0.1 (2021.1.25f1)

Notes:
-Selecting the first corner had different Corner setting when selecting it first or selecting it after the second corner ("Settings.mp4")