Their conclusion is that in big O notation, quantum annealing and best classical algorithms are the same.
Parallelization would get you a factor 1/k (k being the number of cores) in favor of the classical algorithm at best, which specialized hardware would give you a constant factor boost without affecting the big O characteristics.
The problem is not "which is faster given a fixed n". Quantum computers are interesting for certain problems when n becomes larger and larger.
The real issue is whether if there is an exponential difference between quantum annealing and classical algorithms or not, in big O notation. Remember, that is the reason why people are so interested in quantum computation. Not some constant speed up.
O(f(n)) vs O(log(f(n))) and O(f(n)/k) vs O(log(f(n))) are essentially the same in terms of their capabilities of solving NP problems.