Causality optional? Testing the "indefinite causal order" superposition

Over a decade ago, when I was first starting to pretend I could write about quantum mechanics, I covered a truly bizarre experiment. One half of a pair of entangled photons was sent through a device it could navigate as either a particle or a wave. After it was clear of the device, the other half of the pair was measured in a way that forced the first to act as one or the other. Once that was done, the first invariably behaved as if it were whatever the measurement made it into the whole time.