The paper itself says the only change is normalizing by the context window size C.
What if that's the real reason for their sometimes slightly-better, sometimes slightly-worse performance on some benchmarks? Perhaps there are other changes, too.
This is why I continue to think Gensim's policy of matching the reference implementations from the original authors, at least by default, is usually the best policy – rather than using an alternate interpretation of the often-underspecified papers.