I don't know if I've thought this comparison through completely but it was fun thinking about it...
Think of a film's characteristics as a trail up a mountain - there's a small foothill section and then the trail gets steeper but maintains a steady grade for a long time. Now imagine another trail going up a steeper hill - but starting with the same foothills.
Now imagine hiking up both hills keeping track of distance and elevation gained.
On some walks, start counting the distance at the trailhead. On others go past the foothills and start counting. Starting after the foothills and hiking a certain distance will get you more elevation gain than starting at the bottom and hiking that same distance. Because the foothills were gentler, you didn't gain much elevation from that part of the hike when you started at the bottom. Those are your shadows.
The distance you hiked is your subject brightness range. How high you reach in elevation (highlights) depended on how steep the hill is (contrast) and how far you hike (subject brightness range) plus where you start from (exposure).
Developing longer, makes the hill steeper.
Here is an illustration of Tmax 400 in D-76 1:1 characteristics. Each gray line is a different development time, longer development time makes a steeper curve. I imagined your photograph and marked it in Red.
If you only develop longer, you will get to the Blue line. If you increase exposure AND develop longer you will get to the Green line.
Notice Blue and Green are similar. They would both make prints that even an expert would have a hard time to tell apart. I'd rather print from the Green line.