I suppose when attempting to reduce such a group to a simple catchphrase ("post-emotional"), no additional harm is done by throwing those who were 21 in the year 2000 with those who were five.
My opinion is that it's always difficult to describe phenomena while inside; easier to categorize the mood of an era once the era has passed.
As someone born in 1981, I've ended up in all sorts of buckets. Sometimes '81 is considered the tail end of Generation X. When I was younger, I thought of myself as solidly Gen-X, because "my" culture all seemed to be quintessentially Gen-X culture: Nirvana, MTV, skate-punk, the microcomputer revolution, cynicism about both staid corporate life and the hippie alternative to it, etc. Later I realized that many people considered '81 a bit late for Gen-X, but I had considered myself in it because as a teenager I identified with culture-drivers who were actually 5-15 years older (e.g. Kurt Cobain somehow seemed in my generation at the time, but was in fact born in '67). This article, and some others, by contrast would group me as a Millennial, but many of the other descriptions I've found of Millennials seem aimed at people younger than me, mainly people born in the late-80s/early-90s.
Generational theory is interesting on the surface, but often I take these meta-analyses with a grain of salt. They seem to be grandiose astrological interpretations that would be applicable to any generation.
I'm part of the "Nomad" generation type. Nomadic definitely describes my life fairly well for the past 10 years. I've lived in 2 countries and 5 states. The post office should just start OCRing my mail and sending it via email.
To get meta, I think that it's probably easiest to envision generations as phases of an ideological sine wave. At any given time, one set of ideas and culture - one phase - will be dominant and will contain most of the population. However, no phase ever dies out completely - there's always a few oddballs who will find medieval chivalry, for instance, appealing. I think that you and I were just born in between the peaks of Generation X and the Millenial generation, so our values are somewhat harder to predict.