We use Brownian dynamics simulations with hydrodynamic interactions to reconcile the apparent contradictions in experiments on the effect of shear flow on desorption of polymers. Our simulations show that desorption is governed by an interplay between chain-wall attraction and wall-induced hydrodynamic repulsion. When adsorption is weak, the chains form large loops and tails that generate stronger hydrodynamic interactions in the presence of the imposed shear flow, causing longer chains to desorb faster than shorter ones. In contrast, when adsorption is strong, the chains adopt a flattened conformation, weakening hydrodynamic interactions and resulting in shorter chains with fewer sticking points desorbing faster than longer ones. (Figure Presented).