  Experimental data from the NA49 collaboration show an unexpectedly steep rise
of the rapidity width of the $\phi$ meson as function of beam energy, which was
suggested as possible interesting signal for novel physics. In this work we
show that the Ultra-relativistic Quantum-Molecular-Dynamics (UrQMD) model is
able to reproduce the shapes of the rapidity distributions of most measured
hadrons and predicts a common linear increase of the width for all hadrons.
Only when following the exact same analysis technique and experimental
acceptance of the NA49 and NA61/SHINE collaborations, we find that the
extracted value of the rapidity width of the $\phi$ increases drastically for
the highest beam energy. We conclude that the observed steep increase of the
$\phi$ rapidity width is a problem of limited detector acceptance and the
simplified Gaussian fit approximation.
