In the hydration force theories it is customary to assume that the hydrophilic surface is an infinitely thin plane. In many cases, however, the polar surface of a molecule or the surface of the corresponding aggregate is corrugated and soft, the surface/solution interface then being really a deformable interphase. Our theoretical analysis shows that the interfacial "smearing" may strongly influence the apparent decay length of the hydration force between two laterally homogeneous surfaces, representative of polar phospholipid membranes. This length is approximately given by Lambda(eff) similar or equal to d(p) Lambda/[2s Lambda + (1 - 2s)d(p)], where d(p) is the decay length of the interfacial polarity profile, s less than or equal to 0.5 a measure of the interfacial softness, and Lambda the solvent correlations decay length. When the interfacial width is much larger than the intrinsic decay length of the correlations in pure water, and the interface is sufficiently soft, the former becomes the chief determinant of the range of hydration-dependent intersurface force. This introduces new possibilities for the probing of interfacial structure and rigidity in the atomic force or osmotic-stress measurements and provides new mechanisms for the information exchange between the opposing hydrophilic regions.