My money's on blizzard trying to give themselves room to grow. Remember, they just put a lot of effort on this stat squish - it seems natural for them to also do an ilevel squish. They may have not wanted to do that retroactively since it would probably upset people to change the ilevel on their gear in late MOP, but with WoD they have a clean slate to start with.

I am impressed with the gear's stat design in WoD so far. While leveling, it felt more proper than in previous expansions - my MoP heroic-raid geared team didn't immediately start collecting gear that was many ilevels above from the first quests in the new expansion. I got to feel very powerful for the first 5 levels or so, which makes sense because of their high gear level. I also like how I'm still wearing my epic cape and heroic garrosh weapons in WoD normals - I think it's fitting for a few iconic pieces of gear to remain relevant for the first tier of dungeons in the new xpac.