  Following up on a recent paper [Bharti et al., Phys. Rev. A 109 (2024)
023110], we compare the predictions from severalR-matrix with time-dependence
calculations for a modified three-sideband version of the "reconstruction of
attosecond beating by interference of two-photon transitions" (RABBITT)
configuration applied to helium. Except for the special case of the threshold
sideband, which appears to be very sensitive to the details of coupling to the
bound Rydberg states, increasing the number of coupled states in the
close-coupling expansion used to describe the ejected-electron--residual-ion
interaction hardly changes the results. Consequently, the remaining
discrepancies between the experimental data and the theoretical predictions are
likely due to uncertainties in the experimental parameters, particularly the
detailed knowledge of the laser pulse.
