A: It can be either one, or a combination of both. Every time you puff on your cigar the flavors in the tobaccos begin to caramelize and the tobaccos become juicier. As you continue to puff, the juices build up, so, by the time you get to that last third the flavors are naturally stronger. That said, if you draw too hard or too often the juices can turn bitter. As I’ve written in the answers to similar questions, draw slowly and about once per minute.
According to one of my resources, the size of the cut can also impact how concentrated the flavors become as you smoke. A narrower cut naturally permits less smoke through the head, whereas a wider cut permits more smoke and flavor through the head. If you’re not puffing too often or too hard, try clipping the cap of your cigar with a double blade guillotine that will expose most of the tobacco at the head, and avoid punch and V-type cutters.