I think what people are saying is that retracts that move from the leading edge to the trailing edge (P-40, F-4U ect) will have a more significant change to the CG as the gear and wheels move from front to back than if they retract from outside to inside (T-6, P-51, P-47 etc). It depends on what the retracts do as to their impact on moving the balance point with respect to the allowable CG range.

Jaybird