Reproduction steps:
1. Open the attached project "DragAndDrop.zip"
2. Open the "SampleScene" Scene
3. Open the "Test Editor Window" from the menu bar
4. Attempt to drag a prefab by dragging the "Drag Me" button onto the Scene view and observe the Console

Expected result: "SceneDropHandler" is outputted
Actual result: An error and two warnings are outputted

Reproducible with: 2021.2.0b5, 2022.1.0a4
Could not test with: 2019.4.29f1, 2020.3.15f1, 2021.1.16f1 (DragAndDrop delegates not implemented)

Note: other delegates such as HierarchyDropHandler and ProjectBrowserDropHandler work correctly on Windows. On macOS, they only work when not initiated from an EditorWindow.

Error and warnings:
1. TLS Allocator ALLOC_TEMP_TLS, underlying allocator ALLOC_TEMP_MAIN has unfreed allocations, size 27
2. Internal: Stack allocator ALLOC_TEMP_MAIN has unfreed allocations, size 27
3. To Debug, enable the define: DEBUG_STACK_LEAK in StackAllocator.h. This will output the callstacks of the leaked allocations