I think most people would consider 20% basically within the margin of error induced by stylistic and other non-meaningful differences.
For example, it's not completely clear from the post but it seems like the 0.5x figure is from wc -l, which means Python wins a line every time there is a conditional or loop just because it doesn't need a closing brace. That alone might eat up a lot of the 20%, but you would be hard pressed to say that is a meaningful difference.
My surprise from this study was simply that dynamic languages are clearly not much worse than the best-of-breed statically typed languages. Maybe 20% is within the margin or error, but you definitely can't take that as any evidence that Scala is "better" than Python.
The reason I think this is "big big news" is I thought the general consensus had already been reached in academia if not the programming community that "statically typed functional languages are much better". There's little or no evidence of that in the results of this study.
For example, it's not completely clear from the post but it seems like the 0.5x figure is from wc -l, which means Python wins a line every time there is a conditional or loop just because it doesn't need a closing brace. That alone might eat up a lot of the 20%, but you would be hard pressed to say that is a meaningful difference.