Any album full of material that you don't refer to as an LP, can fairly be called a mixtape. That is the standard. A few songs = Sampler/Single. 4-8 songs = Demo/EP. 9-12+ songs = Mixtape.
Its like I heard a comedian say: "Whats with Warehouses? You don't wear it...and it ain't a house!" (works better if you say it out loud, not read it). -- Same basic principle. It doesn't need to be mixed, or a tape, to be a mixtape. Mixtape is now the universal term for any collection of songs, typically by one artist/group, that is not referred to as an album/LP.
Its an Album-Mixtape, but that is too long, so it is shortened to Mixtape, not because the artists themselves are stupid, but because fans are idiots and would likely refer to this Album-Mixtape as a "debut album", rather than what it is: an Album-Mixtape.
Remember how JT put out Game's Album a year or so ago, and you had the Aftermath PR staff in full effect, scrambling, trying to label and discredit it as "a Mixtape"? Same thing.