Too lazy to look it up right now, but i am quite certain that GCL only passed LDK in 'CAPACITY' of wafers (what they could produce in a year) and not actual sales of wafers in megawatts.
LDK could have used its capex to ramp up wafers, but they, unlike GCL, want to become less dependent on only poly and wafer business and expand into cell and module, therefore, if there is more demand/higher asp for one of the units in the vertical, they can ramp that specific one up and cut back on the lowest demand/asp vertical.