Why is the hamza not considered one of the letters of Qalqalah despite possessing the attributes of shiddah (strength/intensity) and jahr (audibility/loudness)?

The hamza is not considered among the letters of qalqalah by the majority of scholars due to the combination of the characteristics of shiddah (strength) and jahr (audibility) within it. This is because of the alleviation it undergoes when it is silent, and the substitution it is subject to. When the hamza is silent, it becomes heavy and its compression increases. If it were subjected to qalqalah, its sound would emerge as if it were ailing. It is pronounced gently, smoothly, and without excessive effort.