Even if the Schrodinger equation does purport to describe the real behavior, the problem with the article is that it assumes that the parallel superimposed states are accessible to us on a small scale, but not on a macroscopic scale.
But in fact, aren't they theoretical states? When it's time to observe a particle or whatever, we don't see all the states. We see one, and we just can't predict which one.
So we cannot observe a cat in two states such as "dead" and "alive" because we can't do that for a quantum particle either.
The parallel universes (PU) interpretation of QM gives a plausible intuitive explanation why. Maybe the Schroedinger equation is solved fully, but across PUs. Since PUs are available, the solution is unhindered by computational complexity (assuming P = NP, which is probably the case).
Cheap and fast splitting of reality into unlimited numbers of branches of parallel futures trumps P = NP.
Another problem with the whole thing is that (supposing the evolution of behavior in the universe to be a computation) the objects in a computed simulation are not aware that the simulation is going faster or slower, because their time is also simulated. If a simulation has to pause and solve an instance of an NP-hard problem, the entities being simulated do not perceive this extra passage of time: that is happening in the simulator's time, not in simulated time!