Not to defend deceptive business practices, but software battery limits are slightly different from a fuel tank being smaller. By not allowing the battery to charge as close to its full capacity, a software size limit can actually significantly improve the longevity of the lithium cells. Batteries sustain the most damage when they’re charged completely to full, and even the best battery management systems can’t prevent all of the damage. This is also why charging speed is significantly slower near the end of a full charge cycle.