Absolutely, 100% correct. The amount of energy stored increases as the coil charges (dwells) until the point that it is saturated, or 'full.' At this point the charging current levels off, and the energy is converted to heat instead of stored (undesirable for various reasons). But the interesting points of comparison is both how much dwell different coils need before they are fully saturated, and also how much energy they have accumulated at various dwell intervals up UNTIL they are fully saturated. So a small coil might only hold say 75mJ of energy and is fully saturated after 3.5ms of dwell. Contrasted with a big coil like the IGN1A which holds >200mJ (crazy!) and isn't saturated until 9ms! But then if you look at the 3ms mark, the small coil might already be close to full with say 65mJ, but firing the IGN1A that early only nets you a 50mJ spark (things aren't linear). I'll try to remember to grab a scope shot at work one day soon to share here, since we're on the topic and all.
EDIT: Er, sorry, apparently we're on page 2 now, and this was answered already, sorry!
Good observation and an important one but for a totally different reason: timing. Let's say you have total control over your ignition, such as with an aftermarket ECU or a 123 distributor or something, and for whatever reason you want to run some crazy timing like 50 degrees BTDC. So you dial things in, charge your coil up to it's max 5ms dwell, and trigger it to fire at 50DBTDC Cyl#1: What happens? BAM! The coil discharges and the energy runs along the HT lead from the coil to the center of the distributor, down the spring pin in the middle of the cap and then into the rotor. But then. . . where's that rotor pointed? Well, it's like 2/3 of the way between the plug wire terminals for cylinders 2 and 1, and if it has the narrow point on it, then it's not touching either. . . and nothing happens! The narrow end is only in contact with the #1 cylinder post for maybe the -10-30degBTDC, and a wider one will buy you up to say -15-45 deg. Make sense?