Exclusive heavy-vector meson photoproduction is a prominent signal in collider experiments with hadron beams. At the highest photon-hadron collision energies, this process is considered as a candidate to constrain the gluon parton distribution function (PDF) at small longitudinal momentum fractions. However, in the framework of collinear factorization, exclusive particle production is described in terms of generalized parton distributions (GPDs). In this contribution, we investigate the connection between GPDs and PDFs at the leading order in ${\alpha }_s$. Our main result is a proposal to quantify the systematic uncertainty inherent to this connection. We put our approach into context with respect to the Shuvaev transform. Our uncertainty estimate can be straightforwardly adapted to higher fixed orders and small-$x$ resummation. The question of extrapolating GPDs to vanishing skewness is paramount for the program of the Electron Ion Collider, notably for the extraction of the radial distributions of partons.