I don’t think Cyril is questioning wether or not it is acoustic, but rather if it meets the guidelines put forward in here. For example, I personally believe the “absolutely no electric guitar” ruling is off, as I know many acoustic versions of tracks that use a clean electric guitar to counter the jangliness of the raw acoustic tone.
And I view the world 'acoustic' as any instrument that doesn't use electrical amplification. This means digital pianos, synthesizers, electric guitars and electric bass guitars are all off limits. This leaves a lot of instruments still available, like everything that doesn't use power to work. You can send acoustic guitar with vocals, or piano, but there's so much more out there. Frankly, just saying 'no electric guitar' is a narrow definition of 'acoustic'.
As for Deadeye's example; if it uses clean electric guitar, I don't think it's 'acoustic'.
Or, I think anything with synthesizers should not be allowed