I fail to see why everybody thinks that something is erased in the famous Delayed Choice Quantum Eraser experiment (see https://arxiv.org/pdf/quant-ph/9903047.pdf and https://en.wikipedia.org/wiki/Delayed-choice_quantum_eraser).
According the paper, the interference patterns that arrive at D1 and D2 are shifted by pi. That is, if you add the interference patterns together, the pattern is the same as the pattern for detectors D3 and D4. Therefore, if you look only at D0, then no interference pattern is visible, not for the photons whose peer arrive at D3 and D4, but also not for the photons whose peer arrive at D1 or D2. This is different from the normal double slit experiment.
Therefore, isn't it equally valid to say that the interference is always there, also for the photons that arrive at D3 or D4? We just don't detect it in that case, because we only look at only one of the possible paths and don't combine them together. It is the beamsplitter BSc for D1 and D2 which makes the interference pattern visible. That is, no information is erased, and there is no need to transfer information from D1/2/3/4 to D0.
Edit: expressed in a different way: if I would remove the D3/D4 mirrors, and let all photons go through to D1/D2, it would clearly show that there is an interference pattern in D0 for all photons. Setting back the D3/D4 mirrors, redirecting 50% of the photons, would change nothing at the D0 side; the photons would still hit at exactly the same place at D0 as before. That is, the interference pattern would still be there, we just would not have enough information to detect it afterwards.
What is wrong with this interpretation of the results? And if this interpretation can be valid, why is this such a controversial experiment?