Exactly true, however he's donating STOCK not money. So he's avoiding the taxation on the stock gains that he would have seen, which could easily have been upwards of 50%. Then, yes, he can be employed by and can expense costs to his foundation - so that money that he's not being taxed on is still within his control.

However, the bigger deal is that he can use that foundation to wield significant power and to distort public policy to his benefit.