FStreamableManager Unload doesn't unload asset hard references

After calling Unload( ) on FStreamableManager, asset hard references are still valid and usable.

1. Download attached project and extract
2. Right click on .uproject and generate visual studio
3. Open .sln and run as Development Editor
4. Open "default" map if not already
5. PIE
6. Press F, which will load async files and create StaticMeshActors with them
7. Press J to call Unload on FStreamManager and look at Output Log. Also notice new StaticMeshActors being created with should of been unloaded.

RESULT:

After calling Unload, asset hard references are still valid.

EXPECTED:

Unload removes hard references.