As the title shows, any time you try to get a velocity of an Actor with InterpToMovement component, you will get a zero vector. This affects both velocity of an Actor and Get method of InterpToMovement component.
Actor is really moving, but this always returns zeroes:
It prevents from e.g. calculating the direction of the object, making the component a useless decorative movement type :c
I believe what you are seeing is inherited parameters from the UMovementComponent that are suppose to be hidden through code. Velocity isn’t part of the InterpToMovement node because it is literally interpolating between different points.
I have added JIRA UE-41547 for this issue. Our developers will be investigating further. Follow that link to monitor the status of the report.