"Once a person’s heart has stopped beating, it is no longer contracting and pumping blood throughout the body to major organs.A person in this condition will not benefit from an AED that delivers an electrical shock."

Okay, I see what you are saying, but this is oversimplified to the point of inaccuracy. They are trying to say that cardiac arrest = flatlining = asystole = don't shock. Which is what I've already explained, but doesn't tell the whole story.

However, asystole is NOT the only rhythm of cardiac arrest. Ventricular fibrillation and ventricular tachycardia ALSO cause cardiac arrest because they are not rhythms that perfuse blood throughout the body.

"Cardiac arrest is caused when the heart’s electrical system malfunctions. The heart stops beating properly. The heart’s pumping function is “arrested,” or stopped.
In cardiac arrest, death can result quickly if proper steps aren’t taken immediately. Cardiac arrest may be reversed if CPR is performed and a defibrillator shocks the heart and restores a normal heart rhythm within a few minutes."

https://www.heart.org/en/health-topics/cardiac-arrest/about-cardiac-arrest