As far as North American smokeless powder mfg., it was only some of the older (and likely by now discontinued, or likely soon to be discontinued) IMR shotshell powders which were single base. All Alliant powders are double base. All ball powders are double base.
If burn rate is a concern, albeit that this should have been implicit from the onset, then think of this as a case whereby both the flake and the ball sit in very close proximity within the burn rate chart.
Retardants are likely shared in common, albeit that the degree of retardant likely differs from flake to ball for a given burn rate.
But the issue being raised involves the inefficiency of burning a sphere vs. burning a flake. And the contention (prefaced with 'might' as well as with 'generality') is that at low pressures a flake will burn more consistently (with regard to temperature extremes) than will a ball.
