  The velocity dispersion of globular clusters (GCs) around ultra-diffuse
galaxies (UDGs) in the Virgo cluster spans a wide range, including cases where
GC kinematics suggest halos as massive as (or even more massive than) that of
the Milky Way around these faint dwarfs. We analyze the catalogs of GCs derived
in post-processing from the TNG50 cosmological simulation to study the GC
system kinematics and abundance of simulated UDGs in galaxy groups and
clusters. UDGs in this simulation reside exclusively in dwarf-mass halos with
$M_{200} \sim 10^{11}$ M$_{\odot}$. When considering only GCs gravitationally
bound to simulated UDGs, we find GCs properties that overlap well with several
observational measurements for UDGs. In particular, no bias towards overly
massive halos is inferred from the study of bound GCs, confirming that GCs are
good tracers of UDG halo mass. However, we find that contamination by
intra-cluster GCs may, in some cases, substantially increase velocity
dispersion estimates when performing projected mock observations of our sample.
We caution that targets with less than $10$ GC tracers are particularly prone
to severe uncertainties.Measuring the stellar kinematics of the host galaxy
should help confirm the unusually massive halos suggested by GC kinematics
around some UDGs
