Seriously? Is this the quality of discussion HN is regularly becoming? You want me to make an assumption? Is that how you operate in conversation - assumptions to fill in the gaps when something isn't clear?
You realize that their saying "natural" or "unnatural" completely changes what they're saying to the polar opposite, right?
So now clarity is pedantic?
Seriously?
If HN had subreddits there'd be one similar to /r/WatchRedditDie
Literally no one, including the authors of this paper, contends the sequence is "unatural".