Tree Muscles is important concept to me. It is adaptive growth by the witness-able loading. Strong evidence of the wonder of tree's differentiation of parts; that wood is not just generic putty but specialized by position. Being able to catch glimpses of this; is great for instilling respect of trees as life, and an introduction/ parallel/ re-affirmation of other such specialized positions of branch collars, root collars, tops/tips etc. to wonder at, respect and be aware of; to deal with the tree more appropriately with these observations and more feel for trees as a familiarity of life. Instead of as a familiarity as dead wood you can carve and hammer nails into etc.
Usually we think of trees and limbs as round. Round being the most unleverageble shape, in that there are no short axises across a round shape, so there are no weaker axises. For a circle by definition has equal diameters from all angles. This limb is more oval; longer on the vertical axis it supports, than the horizontal axis. For the immense length and angle (horizontal/ parallel with ground is worst leveraged angle), gives massive loading vertically, so that is were the adaptive growth increased the length/leverage to give support. Our smart tree is using it's food and resources most wisely to maximize growth on this needed axis and forsake the across /horizontal axis, making cross-section of limb tall and narrow.
In removing the limb, this gives less turn ability on a hinge, for a pull to the side by hinge would come from the leverage of the hinge on the horizontal axis, that this tree limb hasn't grown very much of. For it has forsaken the supporting growth on the across / horizontal axis that would give good turning ability, in order to grow the taller than wide, vertical axis of support against the massive loading.