[PvK]

The only reason is the game might not be programmed to check for such things.

Training? I imagine with the moon training bug, this would allow stacking ships to instantly train to the max. This might not be so bad, though, as you could thus attach a maintenance cost to training, representing the cost of pre-training crews for ships, which is perhaps slightly more logical than having to build ships and then train their crews using the actual ships.

PvK