I think that's more to do with spring rates than anything else,
The dual port gates are good as you can neatly balance them and keep the gate shut rather than rely on pure spring pressure.
It cant reduce lag though really, once any gate is closed and stays closed you are relying on the physics of the turbo in terms of lag, if changing has made it spool faster etc, then the exhaust pressure must have been pushing the gate open I would guess.