How does one drive a wood screw to a get a perfect-fit thread, as in the first image?
Note the difference between first and second images.
The 'bite marks' that would have been made in the upper part of the thread during driving look like they have disappeared, as if the wood has tightened around the unthreaded portion of the screw.
I've noted comments regarding different wood species, and end grain vs transverse grain. However, I'm still puzzled by the appearance of the first image, examined by itself.
Is the wood grain around screw threads dynamic enough to stabilize a screw over time?
My only guess how this would happen is that there was compression of the wood while driving, then subsequent re-expansion over time (under the influence of internal moisture flows).