Reproduction steps:
1. Open the attached project ("case_1251767-FolderReferences.zip")
2. Open the repro scene ("SampleScene")
3. Open Addressables Groups
4. Notice that inside "Packed Assets" group there is a "SomeFolder" addressable folder with "SomePrefab" inside
5. Select the "GameObject" object in the Hierarchy
6. Assign the "Test" AssetReference to "SomePrefab" by dragging the prefab asset from Project tab to the field
7. Inspect Addressables Groups again

Expected result: "SomePrefab" remains inside "Packed Assets/SomeFolder"
Actual result: "SomePrefab" is moved to Default Local Group and is marked as addressable

Reproducible with: 2018.4.23f1, 2019.4.0f1, 2020.1.0b12, 2020.2.0a14
Reproducible with package versions: 1.1.5, 1.9.2

Notes:
1. The issues do not reproduce when assigning the AssetReference by using the Inspector tool or by dragging the "SomePrefab" from Addressables Groups window
2. Unmarking the "SomePrefab" asset from being addressable moves it back to the Packed Assets/SomeFolder" place inside the Addressable Groups