That's pretty much the kind of problem they're using here. The problem is that to verify the simulation, you need to run the simulation on the classic device, and that requires time that is exponential in the number of particles being simulated. They've verified that the classical and quantum simulations agree for n=1, 2, 3, ..., now here's a quantum simulation for n that would take 10^25 years to do classically.

If what you are simulating is a physical system, then to verify it you only need to replicate the physical system, not rerun the simulation on another device.

I suggested simulating the experiment of n molecules in a vacuum, another experiment might be a chaotic system like a double pendulum. Although there would need to be a high level of precision in setting up the physical parameters of the experiment.