The other way around, as I understood it.
If you buy it anywhere except the CoG-Store, you can get access to it at the CoG-Store.
If you buy it on the CoG-Store, you don’t get access anywhere else (because there they can’t control the accounts and their access, I presume).
As an aside, that’s good to know. Until now I never bothered to keep the receipts.
@jasonstevanhill
In that regard, what is better for you?
Buying it at your store where you get the full price, or at Google / Steam where you get the additional exposure through the sales?