In a recent paper [Physica E 116, 113769 (2019)], Yuriko Baba and Marta Saiz-Bretín study electronic transport in graphene/ferromagnetic insulator hybrid devices. The system comprises an armchair graphene nanoribbon with a lens-shaped EuO ferromagnetic insulator layer deposited on top of it. When the device supports a large number of propagating modes, the proximity exchange interaction of electrons with the magnetic ions of the ferromagnetic insulator results in electrons being spatially localized at different spots depending on their spin. They found the spin-dependent electron focusing is robust under moderate edge disorder. A spin-polarized electric current can be generated by placing a third contact in the proper place. This opens the possibility to use these effects for fabricating tunable sources of polarized electrons.