From Betz limit and power available in the wind
Miles L. Loyd used “drag power system” expression because of the drag induced by the turbine aloft slowing down the wing. After that the two expressions are now used in scientific literature.
A “drag power system” designs a flygen but could also apply to rotary systems like Kiwee, Daisy, Sky Windpower’s autogyro-helicopter, SuperTurbine ™ and other rotating devices, even HAWT. It is a reason why I would prefer to use “torque power systems” terms instead of “drag…”.
Indeed AWE is perhaps the one of the two fields with numerous patents, categories, publications, conferences, before any practical existence, the other field having been the space conquest, but with a more uncertain outcome.