Comparison is made to a recent full-dimensional anharmonic treatment and the most recent experimental . One can see that none of the predictions from this work supports the multiply refuted recent IR-VUV result and interpretation. AC2 comes closest but its focus on monomer anharmonicity is likely to perform poorly for the lightest, strongly librating hydrates, i.e. water dimer. All others consistently predict the water donor OH stretching downshift some 20 cm -1 above experiment and above the full-dimensional variational treatment, perhaps again a consequence of the particularly light and thus delocalised nature of the binding partner. This is also qualitatively true for the second-lightest case of formaldehyde (FAH, Figure ). It is encouraging that the three particularly successful independent approaches based on a harmonic reference are so consistent for such an extreme testing case.