How to reproduce:
1. Open the user's project
2. Open the scene "TestA"
~it has a script which loads "TestB" scene when pressing Space~
3. Play
4. Open the Memory Profiler, Detailed, Take Sample Editor
5. Inspect Assets > Texture2D, it clearly has some sprites
6. Return to Game Window and press Space (it loads SceneB)
7. Take Sample Editor again
8. Inspect Assets > Texture2D, also has sprites, even though there are none in the scene

Expected result: Assets can be unloaded after switching the scene and Resources.UnloadUnusedAssets();
Actual result: Texture2D assets cannot be unloaded

Reproducible with - 2019.1.0a5, 2019.1.6f1, 2019.2.0b5, 2019.3.0a5
Not reproducible with - 2017.4.28f1, 2018.4.2f1, 2019.1.0a4 (some assets can be unloaded)