What about the AP-Calc student that has "merely" practiced hundreds of integrals and is therefore equipped, not just to pass the examination, but to use integra

What about the AP-Calc student that has "merely" practiced hundreds of integrals and is therefore equipped, not just to pass the examination, but to use integrals as part of more complex theories down the line? If they know only enough to apply the concept successfully without knowing its fundamentals, have they "understood" it?