  With the imminent construction of an electron-ion collider in the USA, both
saturation physics and nuclear shadowing physics will be important for the same
processes for the first time. In particular for exclusive production of vector
mesons, such as the J/$\psi$. In this paper we investigate the underlying
assumptions commonly made when phenomenologically investigating this process
from a shadowing and saturation perspective respectively. We use the bSat model
which is commonly used to describe saturation physics, and a calculation by
M.G. Ryskin which is commonly used when describing nuclear shadowing at leading
twist. It is expected that the bSat model is equivalent to Ryskin's result in
the hard scattering and non-relativistic limits. By explicitly taking these
limits we show that the bSat model does indeed become equivalent to Ryskin's
result. However, two more approximations are needed for this result. Firstly,
the factorisation and renormalisation scales in the bSat model has to be
independent of the dipole radius, and secondly, we need to omit a term in the
overlap between the vector meson and virtual photon wave functions. We show
that for the typical dipole radius of the J/$\psi$, the different
approximations off-set each other and the bSat model agrees very well with
Ryskin's calculation in hard-scattering and non-relativistic limits.
