All your Aeroplan points are liability in AC's books. The more you use, the better it is for them. However, when they allow people to pull revenue seats at the last min and convert them into reward seat, that takes away a seat that can potentially be sold as full Y. They wanted Elite to get full fare Y instead of using their points for last minute travel.
They are putting out this double miles thing as an attempt to make people use up their points faster. It's not because they wanted to give greater access to rewards seats to E.
Watch for this benefit to be available to general members really soon.