I have not worked specifically with kingwood/camatillo, but have worked with plenty of other dahlbergias; mostly African blackwood & cocobola, as well as a few of the others. Wendell Castle gave me my only stick of BR, but that is another story.
Anyway: straight grain wood of most species that is as dry as aproximate equilibrium with local current relative humidity, is very stable.
Change the equilibirum, and straight grain wood will eventually swell a little, or shrink a little but mostly stay straight.
That is why the early old masters, who grew up working wood, like Herman Rambow & George Balabushka mostly used straight grain materials or re-used old blanks (Titlist e.g.) made by old people who knew wood and wood grain.
Nowadays straight grain material barely exists in extended lengths for exotics. Gnarly grain also tends to be "prettier" and more interesting. Blanks with a lot of sapwood are among the less stable, but some people love the striking effect. Many exotics are acquired as "turning blanks" which are essentially the re-sized scrap wood and off-cuts from larger boards maybe used for veneer or such. These can be very attractive, but often contain the least stable material as an engineering proposition and may include areas of radical brash/cross grain that is not particularly strong, though gorgeous in appearance.
The short answer is if you can read and understand wood grain from long use, your experience will tell you whether a particular part ought to be cored, or whether it might be fine as a solid stick. Coring is not a cure-all either. And a moisture meter and RH meter in the shop really are useful tools. If you don't understand balanced wood construction, a core might even be counter productive in some cases though it can be a good way to control mass location in a cue.
Dahlbergias are dense and oily, so it takes a fairly long time to absorb or release moisture, and it does not shrink or expand much anyway. However, if the climate changes or if it was not really at equilibrium MC compared to the long term environment, it will move. Straight grain a _LOT_ less that gorgeous attractive grain, which also moves in unpredictable ways that may (likely will) include "warping".
I really don't like A & B joints, they offend me as a traditionalist. :grin-square:
However, they are a smart engineering compromise that uses short sections of, shall we say, "difficult" wood in a way that helps the cue-maker control warping by dividing potential long term change or stresses into short sections so they have less effect overall on the straightness of the cue. You still should be able to "read" wood and know what you are doing. On top of that the best approach is to arrive with a lot of inherent luck.
Alternately, the full splice was a method orginally designed to work with poor old-time glues to make very strong, durable, balanced product that helpd control warping by the methods of the day: Use balanced (uniformly dense cross section) straight grain materials and splice-together shorter sections both for weight balance and for structural integrity and stability.
clear as mud, right?:thumbup:
smt