Hi @johan28 , you are correct that the correction is supposed to be applied to any composition that has H2O in its structure. However, it only applies when there are whole H2O units in the formula. LiOH would not receive this correction because int(0.5)=0.
It is definitely possible that this correction will be erroneously triggered on some materials that contain H2O units but are not really hydrates. However there is really no way to tell from the composition, we would have to do much more sophisticated (and computationally slower) inspection of the Structure to make a more educated guess about when we have a hydrate vs. not.
When developing MaterialsProjectAqueousCompatibility, we decided it was importnant to keep the correction scheme composition-based (rather than structure-based), and we made a judgment call, based on looking at predicted vs. experimental Pourbaix diagrams, that it was better to err on the side of applying the correction whenever we saw H2O in the formula and risking some non-hydrates getting it than to risk missing applying it to hydrated structures.
I hope that makes sense.