It's not obvious to me that there is double counting. The study says, "Individual carbon emissions can be divided into personal consumption emissions, emissions through government spending, and emissions linked to investments." Someone needs to be accountable for corporate emissions, and that someone is the owners. That's entirely reasonable.

If a dollar is spent by a corporation on a person, and that person uses it to buy something else that took carbon to produce, yes, you could imagine double counting the emission. But that can be fixed simply by rolling up the carbon emission to the ultimate consumer: a person, a government, or the owners of a corporation. Corporations can pollute by themselves: buying and using corporate jets, for example. Those can't be attributed to upstream consumers.

If anything, this undercounts the emissions of the super rich, since they also are responsible for a good portion of government spending, too--either directly, because of the outsize taxes they pay, or indirectly, because of corporate taxation of profits of companies that they own. But since they don't control that government spending (at least in theory) it seems OK to not attribute it to them.