I'm not sure if it really helps much. If they want to save time, they should just have people stop introducing themselves like we care who they are and what realm they're on. Although, announcing that you're from Moonguard means that I can just ignore your question (bunch of RP nerds), so that's probably not the worst thing.
I'm not surprised by this and I'm pretty sure Blizzard had already stated that they would only be for Legion. The artifact weapon traits are essentially Blizzard's Legion equivalent of WoD's Draenor-only leveling passives. The idea is that they can give you bonuses for a specific expansion and remove them afterward. The point there is that your character doesn't get infinitely more powerful (each expansion having added more and more power), which would require them to potentially squish numbers constantly. To be fair, each expansion will give you a boost over older content given that your level is higher.