The well-established vapor-pressure isotope effects (VPIEs) are independently corroborated in the set of isotopes H2O-D2O-T2O by the recently proposed congruent vapor-liquid (CVL) diagram only at the vaporization of liquid (l) phase. The striking discrepancies with the expected IE-trends following from the Bigeleisen-Mayer formulation at the condensation of vapor (v) phase have been revealed. The obvious failure of the classical second virial coefficient determined for dilute gas (g) phase to represent the actual predominance of repulsive collective interactions between particles in the so-called overheated v-phase (termed the interphase by CVL-methodology) needs the additional experimental and/or simulation confirmation. This conclusion corresponds qualitatively to that obtained for pair interactions in the about ideal-gas v-phase by Van Hook, Rebelo and Wolfsberg. The crucial distinctions between the fluctuation CVL-diagram and the deterministic, mean-field (mf) by nature, description of the first-order phase transition by its vapor-liquid equilibrium (VLE) diagram are discussed. (C) 2018 Elsevier B.V. All rights reserved.