Ungrounded Lightning Rod,
What you say it true, if you mean about half.
Engineering Instrumentation project documented AH required to start a vehicle.
We plotted current, voltage, start time. Interesting facts:
Some vehicles can be started in 0.1 sec! To count it as a start required generator charging battery after the start. Many vehicles can be started in 0.5 sec. These vehicles are predecessors of start/stop showing up in vehicles lately.
My vehicle requires 3-5 sec to start.
Documented enough vehicles to know any generalization I make an exception can be found.
With that said, initial starting current can be well over 400a (some may not even hit 200a), dropping down to 300a, with high and lows with each compression/exhaust stroke on the engine, current varies about 30 to 50% (saw tooth shaped). Currents dependents on gearing, starting motor, wiring etc. Same model vehicle can easily have 20% different currents readings.
Point here is a 60ah battery can be expected to deliver 200a without harm if done right. Batteries are systematical, can be charged just as heavily as discharged. Always assuming you know what your doing. Very dangerous if you don't!
Have fun,
Scott.