We compare the angular dependence of the pinning of equivalent columnar defects in GdBa₂Cu₃O₇ thin films and a thicker YBa₂Cu₃O₇ single crystal. The tracks' related enhancement of the critical currents is much smaller for the case of the thin films. We interpret this thickness dependence as resulting from a competition between the pinning of the correlated structures, related to total sample thickness, and surface boundary conditions, which force the vortices to depin from the columnar defects near the sample surface.