It's not true, unfortunately. Switching topologies on the amp itself or the HD is the same. You're just using the HD as digital control over the output stage of the amp. The reason for the noise is because the bias circuit voltages have to be changed in a major way, and the ramp up/down in voltage gets amplified. I just use amp models with the same topology within a song usually, or live with the pop/delay which probably can't be heard over our bashing drummer anyway!