Perhaps the wave function always collapses no matter what, but the way it collapses changes? If there was no screen for the photons to interact with they’d continue to act like waves but since there’s a screen they collapse at some point on it dictated by the wave. And if you try to observe how they end up there you end up collapsing it earlier so where they go are dictated by the earlier state of the wave.
Perhaps the wave function always collapses no matter what, but the way it collapses changes? If there was no screen for the photons to interact with they’d continue to act like waves but since there’s a screen they collapse at some point on it dictated by the wave. And if you try to observe how they end up there you end up collapsing it earlier so where they go are dictated by the earlier state of the wave.