[2D] Editing Spline for Sprite Shape Prefab is sluggish

Editing Spline for a Sprite Shape that is a prefab is sluggish compared to a normal Sprite Shape that is not a prefab

Steps to Repro:

1. create a new Sprite Shape in the Hierarchy
2. click on the Sprite Shape and click on Edit Spline in the Inspector
3. edit the spline in the Scene (the spline should change shape smoothly)
4. drag the Sprite Shape from the Hierarchy into the Assets to make it a Prefab
5. click on Edit Spline in the Inspector and edit the spline in the Scene

Result: The spline shape change is choppier than before.
Expected: The spline should change shape smoothly.

Alternately, just open up the SSPrefab_test Scene on the attached project and Edit Spline for the plain Sprite Shape and then do so again for the Prefab Sprite Shape.