Look again from this viewpoint.
The board on the left has more than 40 rings per inch and a very low proportion of darker latewood. Usually this wood, although pleasing to the eye, is not very dense. I envision a tree fighting for light under a closed canopy and it just never got much ooomph going.

The righthand board has a large proportion of latewood. The latewood cells are thick walled, dense and strong. The ring count falls within normal growth range, this was a good tree, it would grade as dense. Look at the right of the board as the tree ages and had to fight harder for food and light. More rings is better is another myth. A good dense piece of wood is usually what you want. Weight generally equals wood, so strength.

Resin production is an injury response and knows no season. These are the epithelial cells (resin ducts, sometimes visible to the naked eye) being triggered by some trauma. In grading classes they teach you to find the cause of massed pitch when you see it. I've seen it accompany timber breaks, shake, borer damage and nothing. I've also heard that what we call fatwood or lighterd, a truly pitch filled tree found in the woods, is the result of lightning. I can't say on that.

Tracing the resin ducts is one way to see slope of grain.