I will try to resolve. I re read your post carefully to try to figure out just what is the variance in you concepts.
The first paragraph is pretty much accurate. The FST and the bound water are important primarily in the first drying of wood. With the exceptions of a few underwater applications woodworkers never worry about the free water. If wood has water above the FSP it is considered Green even if it is being rehydrated.
I think the main misconception in some woodworkers is the degree of reversibility of the process. Wood can be rehydrated and even turned to mush with water, heat etc. below the FSP about 20% the water bonding to wood is still completely reversible.
You can chart the % moisture relative to the humidity as long as you give the wood time to equilibrate.
This equilibration concept causes a lot of the misunderstandings. Various finishes slow the process but none stop it. The only way to do that is outside our scope in this discussion. You can replace the water with other chemicals most often PEG or fairly long chain polyethylene glycol polymer. More complex chemical meddling with the glucose can create viscose or rayon but that is a whole topic. You can probably search Wikipedia on cellulose etc.
The water does come and go by making weak hydrogen bonds to the OH an O in the glucose molecules of the cellulose. This is Also completely reversible as long as there is cellulose and water.
Now you lauded to the changes in the properties of wood as it takes on mor or less water. First cellulose/wood gets softer and weaker as it takes on water or as you entwined harder as it loses water. We call it drying but below the FSP the wood is "dry" as the water is all bound. The wood also becomes a bit more elastic as it takes on water. These properties are used by woodworkers to shape wood and turners at least do a lot of their cutting when the wood is still 20% + or green as it easier on the tools. It also is done because of the other key property do wood and water.
Wood fibres, tracheids or vessels is the change in dimension with change in moisture content below the FSP. Fibres and boards change in width but not much in length. The organisation of the fibres in round structures called tree stems or logs accounts for the variability of the deformation in the wood as it "dries". Most of the cells go up and down the tree but some (eg the rays that are prominent in oak) go from the carter of the tree to the bark or phloem. Trees can carry the amount of cellulose in an area of the tree under compression so the density varies in various parts of poor quality logs. The wood around a knot is more dense and therefore different properties that the main wood.
Another variation in the cellulose structure can be best seen in a very ring porous wood like oak, elm ash, chestnut etc. the spring vs later season wood has markedly different properties.
These and a few more factors contribute to the dimensional change of wood as its moisture level changes. Where the wood is cut from the tree is the largest fact. You mentioned that most woods change in length almost twice as much tangentially as radially. This is the cause if simple cupping. The tighter the growth rings in radius the more the wood will cup for a given width. The rest of the ovemets are all variations on the theme. Different areas want to ove differently and they pull the board to a new shape.
Maybe enough . The most important statement for this discussion is that the water adsorption and loss is reversible forever. We find ways to work with it if we understand it.
I have a background in biochemistry and botany but that was long ago. I have tried to be clear but sorry if it's not.