Growing up, I didn’t really question why this band would be played along side Nirvana, Bush, Soundgarden, Linkin Park, etc. because my radio station of choice was not just grunge, but also “adult alternative.” So it would play pop shit, too, sometimes.
But I still, to this day, often find U2 listed among grunge artists, or their songs get played on grunge playlists. The fuck? How is this shit grunge? It doesn’t fit in any way! It doesn’t have the sound, it doesn’t have the style, shit it doesn’t even have the same emotional resonance. It’s happy and hopeful.
Possibly the same way Fallout Boy and System of a down can be grouped. There is a phenomenon in music ‘similarity’ systems (remember Pandora?) that, because the process of actually analyzing music and classifying it is work, tries to offload the work to elsewhere, and often what really happens is things get grouped not by qualitative similarities like mood, rhythmic complexity, tone etc. but by the quantitative and easy ‘these two were liked by the same group of people, aged X~Y, so they must be similar.’