Doubt it was the tube rolling that fixed those cracks. Toe cracking is almost always a heat and travel speed thing, or your fitup had a gap you didn't notice. I've run the same cheap wire for years on ranch gates and trailer frames, never rolled a thing, and my welds hold fine. Rolling tubes changes the arc feel a little, sure, but it doesn't magically make a bad joint good. You probably just slowed down and paid more attention once you started messing with it, and that's what saved you.