I don't know if there is a technical name for it.
When trying to get these modelled with FC Gear Toolbox, I have read a lot of technical documentation about gears theory too get help, until my brain melted.
Result was, that nothing like this seems to be technically relevant, otherwise somebody would have described this before.
And true: you can't use them to transport torque, as the side of the teeth is also where they are sleeved.
So I helped myself: You are right, they are helical extruded shapes, with a circular extruded shape as outline limitation. Otherwise you can't use an inner gear, as the teeth of it would bang into the holder structures.
And that resulting shape is not perfectly fitting. You could write masterthesis to get these shapes correct. For a cool looking gadget it works my way.