University of Goteborg research (link)

As shown in Table 10, water absorption decreased at water leaching due to acetylation. The effect was greatest for Eucalyptus cloeziana. The hydrophilic hydroxyl groups
The cell walls have been blocked by more hydrophobic acetyl groups, and less water can be absorbed. This effect is strongly linked to the dimensional stabilization effect, because the swelling is due on water absorption in the cell walls. The decrease in water absorption is not as big as the decrease in swelling, which is because the wood still can absorb water in cavities such as cellumina and vessels. The increase of water absorption obtained in the other The lacquer cycle probably was due to a difference in the experimental performance.

https://gupea.ub.gu.se/bitstream/2077/47743/1/gupea_2077_47743_1.pdf