I think the author means to say, "Since physicists input initial states to get to a meaningful output" or "Since the physicists assume cause and effect are sequ

I think the author means to say, "Since physicists input initial states to get to a meaningful output" or "Since the physicists assume cause and effect are sequential", it leads to the grander assumption that Universe is a giant computer. One way of seeing the Universe is as a stacked geometry of inclined planes in infinite number of permutations and combinations. Physical phenomena like light/gravity/time are just rolling balls on these inclined planes taking any number of paths. Thus pairs of effect-effect or cause-cause are also possible.