ptr: the roof mounted wing in that video is sure to increase drag: it increases frontal area, and is designed to produce downforce. The wake is going to be larger.
As for the mid position wing, the only way one can have any meaningful effect is if the hatch angle is shallow enough that the wing can interact with flow coming off the roof (which is the case for the Pinto - not attached, but also not in "dead water"). It will have little to no effect if it is sitting in the dead water zone, like this Mk 1 Golf/Rabbit:
EDIT: and based on the steepness of the AX rear glass, my guess is the bump on the AX hatchback is cosmetic.