Okay well I tested it at 150d, 300d, and 650d at both 150d convergence and 650d convergence (even made a graphic, but it's not really needed).
The scattering seems to be the same.
What I THOUGHT was convergence was the random scattering of the bullets when they are fired. When you have tracers on it appears that the rounds cross each other, but for the most part that's the random out-of-whack rounds, not the basic direction the gun is pointing.
So, guess I was wrong on that. The tracers are misleading. Good thing I don't use 'em that often.