Are you actually a journalist?
The Army underwent an expansion after 9/11 when it became obvious that is was necessary to move the Reserve component from a strategic reserve to an operational one. Meaning that the Reserves had to be mobilized to meet the shortfalls in the active component caused by the reduction of the military after the collapse of the Soviet Union. There have been tons of arguments about who was to "blame" for this. The bottom line is that it doesn't matter, it is a fact.
After the expansion was approved and begun, the military needed both more recruits and higher retention initially as it was filling positions that did not exist prior to the expansion. We have now reached a steady state and some of the scheduled expansion has been cancelled due to cost. There is neither the same requirement for new soldiers nor the same rquirement for retaining serving soldiers.
For Kaplan's argument to be true there would have to be hollow units, as in the Carter years, throughout the military. Under Carter we had companies with two platoons instead of three and battalions with two companies instead of three. That is NOT the case today.
SLATE should really find someone better to fill Kaplan's role. It can't be that hard.