How to reproduce:
1. Open the attached project "splines"
2. Open the scene "SampleScene" (Assets/Scenes/SampleScene.unity)
3. In the Hierarchy window, select the GameObject "Spline"
4. In the Scene view Tools menu, select the Spline tool
5. In the Inspector window, observe that the Spline Container Edit Mode is set to "Bezier"
6. In the Scene view, observe the handles on the "Spline" GameObject

Expected result: Linear and Bezier handles are seen
Actual result: Linear handles are seen

Reproducible with: 1.0.0-pre.5, 1.0.0-pre.9 (2021.2.12f1, 2022.1.0b8, 2022.2.0a5)
Not reproducible with: 0.1.0-preview.1 (2021.2.12f1, 2022.1.0b8, 2022.2.0a5)
Could not test with: 2019.4.36f1, 2020.3.29f1 (Couldn't import the Package)

Note: Changing the Spline Container Edit Mode to "Linear" or "Catmull Rom" and back to "Bezier" solves this issue