How to reproduce:
1. Open the attached “IN-85814“ project
2. In the Project window (Project → Asset), double-click on the “Test Variant” prefab
3. In the Inspector window, drag the “Test Variant” prefab from the Project window into the ‘Prefab’ field of the “Prefab Reference Test” component
4. In the Hierarchy window press '<' to exit the Prefab Editor
5. Select the “Test Variant” prefab in the Project window
6. Observe the Inspector window

Expected result: The “Test Variant” prefab is assigned to the ‘Prefab' field
Actual result: The 'Prefab' field is set to 'None’

Reproducible with: 2021.3.45f1, 2022.3.50f1, 6000.0.23f1

Reproduced on: macOS (Intel) (user), Windows 11
Not reproduced on: No other environment tested

Notes:

* The bug does not occur if the “Test Variant” is selected by clicking on the 'Prefab’ field directly
* The issue only occurs with prefab variants, not with regular prefabs