  The present work intends to join and respond to the excellent and thoroughly
documented rovibrational study of [X.-G. Wang and T. Carrington, Jr., J. Chem.
Phys. 154, 124112 (2021)] that used an approach tailored for floppy dimers with
an analytic dimer Hamiltonian and a non-product basis set including Wigner $D$
functions. It is shown in the present work that the GENIUSH black-box-type
rovibrational method can approach the performance of the tailor-made
computation for the example of the floppy methane-water dimer. Rovibrational
transition energies and intensities are obtained in the black-box-type
computation with `only' 2-3 times larger basis set sizes and in an excellent
numerical agreement in comparison with the more efficient tailor-made approach.
