Yep, very important. That is why you have to be careful with a toy hauler. Adding weight to the usually rear of the trailer could induce dangerous sway.
I was working with this engineer in FL. He thought he was a lot smarter than he was. Anyway, he hauled a load of household furnishings back to his IN home with a uhaul trailer and he was complaining about that terrible uhaul that would start swaying if he got above 55mph. I had to break the news to him that it was his fault by not putting enough weight on the tongue. Geez, I disliked that guy!