A pinhole camera has no lens. The effect here is like a pinhole camera, but a pinhole camera is nothing at all like a lens. Pinholes diffract light. Lens refract light.

EDIT: Of course you can't resolve an image through diffraction. That's not how pinholes cameras work. Diffraction negatively impacts image resolution, but it absolutely happens when light passes through them. But, although lens do use refraction to resolve an image, that same process also has unintended negative effects on image resolution (spherical aberration, chromatic aberration, etc.). I didn't bring up any of that because it was ultimately a distraction from the important part: narrow gaps diffract light, lens refract light, and pinhole cameras do not work like lens.