John Paul Sanborn
Above average climber
Ok, so, as a novice trying to pick up what you guys are laying down, based on everything I have read on this. Basically, there is no definite answer on the "why" these trees do this, as everyone is different and all are based on situation's at the sites. In other words, its all conditional. That it is up to the individual to investigate each situation, independent of the others. No different than a tree that has a disease, while the same species next to it, in the same yard, does not. Some trees are genetically pre-dispositioned to this, while others are not but still do?
To sum it up, nature has its way?
Deep stuff, genuinely trying to learn/understand! Had to get out the books to understand some of this! But they were not much help, the books I have anyways!
I think you have a basic understanding of what is going on, some trees will have it as a genetic response, others it seems to be more abiotic.
It has been posited that twisty cedar types in inhospitable locations have a twisty phloem because it protects the entirety of the tree from weathering.
Some genera have a "naturally" twisted fiber; anyone who has split Ulmus has seen this, but I have not read any conjecture for the why of this development, evolution is random, and not all traits have a purpose. Many seem to be linked to a different seemingly unrelated mechanism, and may be "useless".
There can be a wide degree of morphological diversity within a seed crop from a single tree, or a wide range of plants that breed "true to form" and a few sports. As you say, it all depends.