There seems to be a widespread misconception about kielwood shafts and moisture content.
Immediately following the torrefaction process the moisture content of the wood is essentially zero. The wood is steamed so as to bring the moisture content back to about 5 percent, give or take. Without that added moisture, the torrefied wood would be prone to splintering or shattering when machined on the lathe.
The torrefaction reduces the hemicellulose in the wood, which results in a reduction in the amount of moisture the wood can absorb from the surrounding air, by about half.
Like a standard maple shaft, a kielwood shaft's moisture content is still determined entirely by its ambient conditions. It's just that at the same ambient conditions, a kielwood shaft's equilibrium moisture content is about half that of a standard maple shaft. The kielwood shaft does not cease to absorb/release moisture according to the ambient temperature and relative humidity. It just has a reduced capacity to hold moisture, so its moisture content in high humidity is less than the moisture content of a standard maple shaft in high humidity. Both types of wood still absorb and release moisture as ambient conditions change.
