No it wasn't. Prot Paladin sword, Shaman shield for elemental and restoration were simple recolors too.
You don't understand, do you? They are not made specifically for NPCs. It's the other way around - sometimes (and only sometimes) NPCs are given unavailable weapon recolors, when it fits. Most of the time NPCs get the same gear we wear. So your point about "well they couldn't be made for NPCs because that would defeat the purpose" is invalid. Because the recolors aren't for NPCs, they are done for more diverse choices for the game designers to choose from.
There are more than 4 recolors for older weapons - some have up to 12. So they most certainly didn't go and make an effort to draw new colors for the artifact, it was already there. I'm sure we can find more recolors for every artifact of each spec than the 4 available in-game, it's just that Blizzard chose four best ones for each one. And in case of prot, that sword had to fill 20 slots, not 4 (5 models * 4 colors each), so they decided to pretty it up a bit so that it wouldn't look completely placeholderish. Unlike the demo dagger, which survived a couple of weeks at best - maybe Blizzard didn't want to hold up an already late spec simply because of some variants still being in the works. If it was released at the start of alpha, it would probably have only the first model option too for all different skulls.