PrefabUtility.IsPartOfVariantPrefab() doesn't recognize variants when a Prefab Variant is inside a non-Variant Prefab

How to reproduce:

1. Open the attached project "IsPartOfVariantPrefab.zip"
2. Select and drag Assets/3 (1).prefab into the Hierarchy window

Expected results: "6: VARIANT" is shown in the Console window
Actual results: "6: NON VARIANT" is shown in the Console window

Reproducible with: 2020.3.45f1, 2021.3.18f1, 2022.2.7f1, 2023.1.0b4, 2023.2.0a2

Reproducible on: Windows 10