It sounds like we're discussing the difference between fandom and obsessive fandom. For me, it comes down to something like this.
Fandom: buying all the albums, going to shows in your city, repping the merch, etc.
Obsessive fandom/geekdom: familiarizing yourself with the deep catalog, thinking about the band when you're not listening to them, traveling to shows/seeing multiple shows on a tour, spreading the gospel to your friends and family, worrying about conflict/drama within the band, spending time on DTF when you should really be working, etc.
Quick DT geekdom story of my own: I was at a party at a friend's house a few years ago when Amazon's Alexa was a new thing. My friend was the earliest adoptor any of us knew, and he was explaining how it could "play anything you ask for" (staight up science fiction as far as we were concerned). We all wanted to test it out, and someone in the room said, "hey Aaron, see if it knows any songs by that band you like so much". So I say "Alexa, play a song by Dream Theater". Alexa happily responds with "playing songs by Dream Theater" and proceeds to play... The Answer Lies Within. After some confused/disappointed looks from around the room, I dejectedly gave a more specific instruction: "Alexa, play Pull Me Under by Dream Theater".