Asking what separates funk from other groove-based music implies that groove is all there is to funk which clearly isn't the case (that's like saying improvisation is all there is to post-swing jazz and labeling any music with a significant amount of improvisation "jazz"), which is why nobody but you considers GG or Can funk bands.
Not really in the mood to try to define funk for you and more than anything else, this thread is illustrating the inherent uselessness of genre tags. But I'll make one last point- funk vs. disco. Too very similar groove-based types of music from the same period but pretty much all knowledgeable music listeners know the difference when they hear it (and no, it's not simply that funk is black and disco is white).
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