This doesn't mean much. Cataclysm was the first WoW expansion you could buy digitally, so retail was a much bigger deal. Now though, almost everyone is buying directly from Blizzard, digitally.
Stand in some bullshit line with smelly people, or push the button that gives you the game instantly? EZ choice. Unfortunately this means there is no reliable way to get sales numbers that are even remotely accurate for this title.
If you're a US citizen, please speak up for the unarmed black American men being murdered every week by the police. It's not about "social justice". It's about human rights.