"Set as first/ last sibling" cannot be undone to reorder the Prefab Hierarchy. Refer the attached video

Steps to reproduce:
1) Create a new project
2) Create a Cube > Drag to project to make a prefab
3) Create a Plane and Capsule as child to parent Cube prefab > Apply all
4) Reorder the Plane and capsule order by > GameObject > Set as First Sibling
5) Edit > Undo or Ctrl+Z

Actual result: Unable to undo "Set as First Sibling" to reorder the prefab hierarchy

Expected result: "Set as first/ last sibling" should be undone to reorganize the Prefab Hierarchy

Occurring in: 2020.2.0a15, 2020.2.0b14, 2021.1.0a8

Working fine in: 2020.2.0a14

Environment: Both Windows and Mac