EXACTLY. It's not a legitimate meal replacement if it's replacing the proteins, vitamins, and minerals you'd be getting from a proper meal with caffeine and fat.
Although I have to say, my mom made me a bulletproof coffee once, and that shizz was straight-up deloycious. But it made me feel like crap afterward.
Well, there's good science for that, actually. Butter makes food more flavorful because most things that impart flavor are fat soluble, so butter allows those flavors to better bind to taste receptors . So I'm sure you can actually get more of the nuance of the coffee by adding butter.
This makes me wonder if there should be like (grass fed!) butter and wine tastings, which somehow manages to be both peak yuppie AND peak fatass.