Ahh, Such a simple subject made oh so murky
The application of simple Ohm's law has limitations here. Since we are dealing with a pulsed, DC fed, iron core inductor there are other factors to consider (reactance,core saturation, ringing etc.) . Add a slow, linear IC regulator etc..etc..etc.
A correction for other "power factors".

For the layperson (modeler/consumer) seeking a relative measure of actual power consumption it isn't really time to dig out a pile of theory . A simple measurement of the current differences with the different supply voltages should suffice. The current will be averaged by the meter and the measurements should help predict the battery running time as closely as needed. For the most part, in this case an increase in voltage will indeed find a fairly linear increase in current flow. Although the current increase with large changes in conditions will not be as linear as Ohm's law may have predicted. That is because OHM's law is looking for a constant resistance (impedance). Not the case in our ignition circuit.

Then again we could stir up some more murk. Perhaps to camoflage a few mis-statements ?

BTW: I miss the CW exam . It helped keep the CBers on 11 meters . Eliminated a ton of the SSB splatter we now have on HF. Too many of those CBers brought their home-brew amplifiers and "transmitters" along with their bad habits onto the HF bands.

DAHDAHDAH DAHDIDAH
DAHDAHDIDIDAHDAH
DAHDIT DAHDAHDAH DAH
DIDIDIDIT DIDAH DIDAHDIT DAHDIDIT
DIDAH DAH
DIDAH DIDAHDIDIT DIDAHDIDIT
DIDAHDIDAHDIDAH [8D]

Ex radio operators are everywhere . One of the most important lessons learned in school is that teachers are often dead wrong.