Does the voice break happen before or after my inner groin hairs start to lengthen?
Think of your body as a set of loosely connected but mostly independent systems. Within each system there is a fixed order of progress, but each can go at their own rate. Thus, the order of body hair development is pretty predictable, as is the order of bone growth, but between the two systems how they line up with each other might be skewed between individuals.
The voice box changes during stage 4 of development, but there is nothing really that comes before or after it to be able to predict when those changes start and end.