It's all relative. We generally don't assess phones by tonal balance, but by driver speed and sensitivity. In other words, resolution is usually what dictates better can, worse can--at least in this community. So since 8 years ago, we have HD800s, Omega 2's, LCD-2s, the HE-series (some of which are really cheap), T1's, and so on.
Pretty much all of them are faster transducers than the HD650. So the scale went up and hi-fi became $1K cans. Cans with less resolution naturally fell to mid-fi, and the worst are lo-fi. It just makes things easier to talk about. It's nothing personal--though I'm not sure why anyone would include a can in their self-identity anyway.
Well one could argue that the Stax SR-009 are true hi-fi and the other cans like the LCD-2/3, HD800, HE-6/500 are really just upper mid-fi if all that matters is speed, resolution, etc. Most agree that the 009 is on another level.