  The observation of massive black hole binary systems is one of the main
science objectives of the Laser Interferometer Space Antenna (LISA). The
instrument's design requirements have recently been revised: they set a
requirement at $0.1\,\mathrm{mHz}$, with no additional explicit requirements at
lower frequencies. This has implications for observations of the short-lived
signals produced by the coalescence of massive and high-redshift binaries. Here
we consider the most pessimistic scenario: the (unlikely) case in which LISA
has no sensitivity below $0.1\,\mathrm{mHz}$. We show that the presence of
higher multipoles (beyond the dominant $\ell = |m| = 2$ mode) in the
gravitational radiation from these systems, which will be detectable with a
total signal-to-noise ratio $\sim 10^3$, allows LISA to retain the capability
to accurately measure the physical parameters, the redshift, and to constrain
the sky location. To illustrate this point, we consider a few select binaries
in a total (redshifted) mass range of $4 \times10^6 - 4 \times 10^7\,M_\odot$
whose ($\ell = |m| = 2$) gravitational-wave signals last between $\approx 12$
hours and $\approx 20$ days in band. We model the emitted gravitational
radiation using the highly accurate (spin-aligned) waveform approximant
IMRPhenomXHM and carry out a fully coherent Bayesian analysis on the LISA
noise-orthogonal time-delay-interferometry channels.
