The title statement is almost meaningless. It would be better just to say "simulating reality takes a LONG time".
My research is in molecular dynamics. I simulate systems up to 1 billion atoms on Kraken & Titan. HUGE approximations are made in simulating these systems, but depending on what exactly it is you're studying, these simulations still provide useful results. That is the key to all these studies: how well does your approximation reproduce whatever it is that you're attempting to model? In some cases, very well. For instance, I'm not going to get exact energy levels of a large system, but the system will qualitatively evolve in the same fashion that the experimental system does (which then guides the experimental counterpart to the research). I don't know the details of this brain simulation, but there is certainly some aspect of it that is not being reproduced anywhere close to real-life, and hopefully this isn't what they're interested in (and I'm sure they know that, but I don't think the article author does).
The very best simulations of reality that we can perform handle at most just a few H/He/C atoms. And an issue called the fermion-sign problem means that the computational power necessary to simulate larger systems scales exponentially with the number of particles. Unfortunately what that means is -- short of developing quantum computers (which are polynomial order for the sign problem) -- we aren't ever going to simulate more than a few atoms with near-perfect accuracy, and certainly nothing like a human brain.
EDIT: Didn't mean for my comment to sound so negative. Obviously, the researchers know exactly what they're doing. I was just trying to dispel the impression that we're close to simulating the human brain.