Should one who is praying a supererogatory prayer prostrate if the Imam and congregants prostrate due to their recitation of the Qur'an, knowing that he is from Morocco and follows the Maliki school of thought?

As long as you are performing a supererogatory prayer and the reciter is not leading you in prayer, you are not required to perform prostration according to the majority of scholars, including the Malikis. The prostration of recitation is exclusive to the reciter and the listener, not the mere hearer. The Malikis stipulated that the listener must be listening in order to learn the recitation and its rules from the reciter.