some more insight.
If there is low impedance, then current can flow.
this happens when a sudden voltage is presented to an empty capacitor.
When empty the cap has low reactance so low impedance.
so it is not about the coil capacitor. being charged or discharged when full.
the voltage change happens at the current maximum,
because a coil has kow reactance when it is charged. then impedance to current flow is low.
so
when the coil capacitor is empty. meaning zero (resonant) volts, the current is maximum.
so this is the lowest reactance/ impedance point, where max current flow is allowed.
So if at this zero volts point, a sudden voltage is present, then large currents flow into the coil capacitor.
thus. indeed the M mosfet changes the voltage rapidly at the max current / zero voltage point of the coil capacitor.
this is 90 degrees delayed. or 270.
the large inflow of cold current happens due to the low impedance point, and having a voltage difference on the capacitor plates.
the cap field needs to be suddenly filled.
so M switches the HC coil from positive to neutral voltage.
but this should represent an increase in voltage of the coil capacitor.
so indeed thr HV- and the HC coil need a common reference point, to create the energy vacuum at the voltage change.
which then create the inflow of energy which is the cold current. the displacement current
from the environment.
so basically everything is floating until the discharge, which actually is a charge.
then, the HV coil should be equal in voltage to the HC coil at the switch on of the M.
if 15V is used, HV should be at 15V.
the inflow happens at the max current point, low impedance, so the a Max current should increase when M switches HC to neutral.