It was invented all the way back in TBC, but it wasn't intentional, it was a bug fix for a quest.
They later used it intentionally during WOTLK and many other games like ESO use it to handle quest progress/passage of time during quest lines/events.
These guys had broke off from blizzard before they accidently created phasing and so instead their solution was to use faction standings on quest completion instead of phasing like WoW or instancing like LOTRO did, which was their solution to the same problem, before phasing was a thing.