Aperture does affect the size/shape (hence I wrote the f-stops ), but lot other shape factors are due to lensing (diffraction, irregularities, obstacles, etc..). Different lenses provide wildly different glare streaks on same aperture shape (which is quite identical across modern high-end DSLRs, hence why people put in custom shape cutouts for "artistic" effect in real-life).
It does not substitute glare mask, which is simple solution to complicated lens simulation.