well some 5piece are actually 6 or 7 if you count the headstock, and then there is the fretboard.
a real one-piece neck is impossible, even an old fender tele, with fretboard and headstock in one, uses a route for the truss-rod and a 'skunk stripe' to close it up.
Having said that the Jem neck is listed as 5piece maple-walnut, but in reality it is three pieces of maple with two tiny slivers of walnut:
pictured RG from ibanez.co.jp
The DNA, DBK and HAM were already three piece, but that was maple-bubinga-maple:
I don't know exactly when the switch occurred for the VWH, but the 2005 brochure lists a 3piece neck.
also have a look at this thread: