Sounds like a bad starter drive. The gear on the starter is part of a one way clutch. It the direction the starter turns the gear and shaft are one. When the motor is going faster than the starter the gear and shaft freewheel allowing the gear to be easily retracted from the flywheel. I am interpreting your noise to be a drive that is free wheeling in the forward direction.
Simply speaking the ignition coil is a transformer. It converts 12v to 35,000v or less, whatever the circuit demands at the moment. BTW no matter how high performance the specs on the coil the firing voltage is only what is necessary to close the circuit over the largest form of resistance (usually the plug gap under load). An ignition in good shape never sees more than 15-20,000v.
Bosch Master, ASE Master, L1
33 years MB technician