  Previous studies of the chemo-kinematic properties of stars in the Galactic
bulge have revealed a puzzling trend. Along the bulge minor axis, and close to
the Galactic plane, metal-rich stars display a higher line-of-sight velocity
dispersion compared to metal-poor stars, while at higher latitudes metal-rich
stars have lower velocity dispersions than metal-poor stars, similar to what is
found in the Galactic disc. In this work, we re-examine this issue, by studying
the dependence of line-of-sight velocity dispersions on metallicity and
latitude in the latest APOGEE Data Release 17, confirming the results of
previous works. We then analyse an N-body simulation of a Milky Way-like
galaxy, also taking into account observational biases introduced by the APOGEE
selection function. We show that the inversion in the line-of-sight velocity
dispersion-latitude relation observed in the Galactic bulge can be reproduced
by our model. We show that this inversion is a natural consequence of a
scenario in which the bulge is a boxy/peanut-shaped structure, whose metal-rich
and metal-poor stars mainly originate from the thin and thick disc of the Milky
Way, respectively. Due to their cold kinematics, metal-rich, thin disc stars,
are efficiently trapped in the boxy/peanut bulge, and, at low latitudes, show a
strong barred morphology, which results in high velocity dispersions which are
larger than those attained by the metal-poor populations. Extremely metal-rich
stars in the Galactic bulge, which have received renewed attention in the
literature, do follow the same trends as those of the metal-rich populations.
The line-of-sight velocity-latitude relation observed in the Galactic bulge for
metal-poor and metal-rich stars are thus both an effect of the intrinsic nature
of the Galactic bulge and of the angle at which we observe it from the Sun.
