2020.3 is coming to end of maintenance and will no longer be supported.
Reproduction steps:
1. Open the attached “Repro“ project
2. Open and observe the “Assets/Prefabs/PrefabVariant.prefab” Prefab
3. Right-click and select “Show in Explorer” from the Context menu
4. Observe the size of the file
Expected result: The size is similar to other Prefabs sizes
Actual result: The size is 100 KB+ and it’s exponentially higher than the other prefabs sizes