Well yes, I mean, all simulations are, right? You put as much real-life data in as you can, but everything's an abstraction unless you're the team from the Devs tv series.
The actual election that happened is not a simulation, at least not the same kind of simulation that was run by Nate.
That qualitative difference is fundamental. It suffers from the same problem when results of simulations are applied to the "real world". The quality of the simulation is paramount, and there's no way to determine whether the simulation is good enough besides assertions that the simulations are really sophisticated and Nate is very smart.
So, the "actual methodology" is not real life, but some abstraction (like, "assume no friction or air resistance")?