KDXRIDER.NET

I know the linkage moves as the suspension compresses and decompresses, but exactly what does the shock do? Does the shock itself move at all or just compress and decompress? Does the linkage allow the shock to basically remain stationary? Curious how it all works together.

While the shock does compress and decompress, it also slightly pivots about the top mount. There is a needle bearing and sleeve in the top shock mount. If you haven't checked it, I suggest taking all of the linkage apart including the swingarm and greasing everything. This should be done at least once a year. Most people ignore it until all the bearings are shot.
Kawasaki was stingy with the grease and they needed to be greased when new. You will be amazed at how much better the suspension works with good condition and well lubed bearings.

KDXs have the knuckle/dogbone positions reversed from this diagram, but the action is functionally the same.

The 1989+ KDX's have a bushing in the top, not a a needle bearing.

It does move, or it would be a fixed mount, like a car or truck (most of 'em) (disclaimer).