I don't understand.
Dwell is measured in degrees. There's 360 distributor degrees in two full rotations of the crankshaft, firing all cylinders. On a V8, there's 45 degrees of distributor rotation (90 degrees of crankshaft rotation) between cylinder firings. 45 x 8 = 360
Unlike points which were more-or-less fixed at 28--32 degrees of dwell no matter the RPM, dwell varies in the HEI systems, less at low rpm to conserve electrical power and reduce heat load, more at higher rpm. Adding more dwell degrees as the RPM goes up, partially-compensates for the reduced time between cylinder firings. At maximum dwell, there has to be a few degrees where the coil primary current flow is shut off. So even if there's ~40 degrees of dwell, there's ~5 degrees of no-primary-current-flow--which is when the spark is created and maintained. No matter what the RPM is, you still have that 45 degrees between firings in which to charge the coil and build magnetism, and then release that energy as "spark".
HOWEVER, if the TIME between firings is very short (high rpm) then even with 40 degrees of dwell, there isn't time for the coil to become saturated and build the magnetic field. As the magnetic field weakens, spark power drops off. When enough spark power is lost, misfire begins.