Just my choice but years ago when I started pulling, My neighbor who had owned a camper for years, from the 50's on up. He clued me in a lot of rules that he practiced and he passed them on to me.
I recall our discussion on how to hook up my safety chain, as in one chain at that time but he told me that the single chain is hooked to the right side of the hitch in the event the TV and camper became separated.
This was that if they come apart, the safety chain would give just enough of a yank to steer the tongue of the camper toward the shoulder on the right side and not into on coming traffic. That single safety chain had to have a breakaway link so it would be able to free from the camper so it would minimize damage when the TV attempted to stop.
On the other hand, he explained that he had two chains and he said they were supposed to be crossed to form a cradle, not so much to hold the tongue up off the road, but to pull it straight with minimal sway.
I don't know if that was written law or just plain knowledge!
I know that I practice that still today and only seems like common sense.
So I'm with the cross the chains crowd!