Your intuition is more correct: it is not true. The relative humidity of the air matters below 100% as well. I think the parent commenter mistakenly assumed that only "condensation" matters, but materials will absorb moisture from the air even if the water doesn't condense. Entropy drives the dispersion of moisture, and some materials are "hygroscopic", meaning they don't merely reach equilibrium with the air, but actually concentrate moisture from the air and get significantly more wet than the air which feeds it water.