The following things apply more to older systems but could happen if there is a defect in a new component.
There are a couple of other things that can cause the magneto system to generate interference at the higher speeds.
One is the coil is starting to break down but has not fully failed.
The other is a failing plug wire or boot that breaks down when the cylinder pressure builds at higher speed causing the plug gap resistance to increase which in turn causes leakage thru the wire or boot insulation.
The coils can get noisey when the speed increases and the magneto shoots more voltage to them causing a partial breakdown of the coil insulation.