I don't know about Pertronix, because it would be hard to run fast enough to give me one, but the GM HEI system uses a sensor circuit in the module that monitors magnetic saturation of the coil. When the coil reaches full saturation, a current limiter kicks in. As speed increases, the dwell time lengthens by changing the power transistor turn-on point which would equate to "points close" on a mechanical system. The turn-on point can actually back up into the induced primary voltage oscillations from the previous cylinder. That's why a regular HEI starts to spark-scatter at around 5500 RPM unless the reluctor is modified. By cutting half the teeth off the reluctor, the induced voltage from the pickup coil is reduced, and the distributors I modify that way go to 7,000+ RPM. They're stock-appearing unless a tech inspector is really on his toes. That change, along with a few other "Sneaky Pete" tricks is why my engines are very much in demand on the "claimer" cars. It's a race class where a racer can offer to buy a competitor's engine for $1,000.00, and he has to sell or forfeit credit for the race.
Jerry
