I have a problem with the situation you describe. That the source of light is producing packages of photons follows your logic that something must be going through two holes. Maybe so, but absent in your discussion is the mention of nonlocal forces, or any reference to quantum transition physics. I may err here, but I see a situation described in100% classical terms, which to me implies the reader, myself included, must not only fill in their own blanks, the must create the blanks in the first instance.
Some have characterized light as coming in two flavors (Feynman "Lectures on Physics") having to do wih polarization inferences. Half the light gas is shared by E fields oscillation 90 degrees in rotation. This is somewhat unsatisfactory by its implcation that each photon is keeping track of all those surounding it to maintain its proper identity. This plus the unbelievability in mother nature producng photons exatctly alike with the exception of the E field direction scheme.
A possible solution to all the objections is the recognition that the polarization experiments imposing the 'dual nature of light', is infact a demonstration of the +/- oscillations of single photons at some natural frequency, probably the measured frequency. When a photon enters a polarizing medium the current state of the oscillations defaults as a measured state. As we are discussing directions of fields and as the polarizing medium is spatially oriented (like Stern-Gerlach arrangements oriented by the direction of the field/gradient direction of the segment) 1/2 half he photons will point outside the angle of their window and become absorbed by the filter, allowing all ohers, now localized to angles determined by the polarizing channels inside the polairizer mass.
In two hole diffraction transitions the "wave-particle duality of electrons" is manufactured to hide an ignorance of what is physically occuring. The electron also with two "spin states" is oscillating such until reaching the plane containing the holes at which time what ever state is "observed" this is the polarized state, with the unobserved state assuming the new task of nonlocal force center.