You are right.That's the theoretical reason but when both chains start from the same point, the odds that the cradle works are astronomically low. I still cross them as it doesn't hurt but I hold little faith they will catch the tongue.
The safety "chains" I had on the tornado was a few pieces of rope that I would tie to the car. Eeek. I didn't really like it but it didn't move all that often so I never bothered making a better system.
The theory sounds good and just makes you look like a professional trailer operator.
However, in order for the theory to work in practice, the chains need to be the proper length or else you are pretty much in the same boar as if they were not crossed.
Here is a good explanation.