Some people need to understand that using this tag is like people who tag things with "indie rock" and not simply "rock". You can use the umbrella term if you like, but that doesn't make this tag any less relevant or useful to other people.
Neo visual kei usually describes visual kei bands with a (radically) new/different sound than old-school and the time between these (old-school and "regular" visual kei) two. Sometimes Neo visual kei bands is also called having a Neo Japanesque these. neo visual kei is quite a fuzzy term, but hopefully this gave you at least a little better understanding of the concept behind the term(s) :)
The old stuff is already differentiated, and this tag is used even for new stuff that imitates the old! I don't see "NEO VISUAL KEI" as a really meaningful tag, but people can't be stopped using it. ._.