This is refering to drag & drop within Blender which is using the
drop-box system.
Previously Escape would cancel the dragging, but still pass on the event
to other event handlers, which could trigger other behavior. For example
cancelling dragging a file in a file browser dialog would also cancel
the file browser operation and close the window. Right-click didn't
cancel anything even though we usually use both Escape and right-click
as a way to cancel the operation.
Now both escape and right-click both cancel the dragging and the event
is not passed on further.
Pull Request: #104838
d58e422ac3