This story could also be titled
"Oops! If you chop people up, they don't grow back. My bad." At 1000 words it's probably about 200 words too long to sustain this joke.
It is an amusing story. Earth gets conquered by space starfish who are expecting humans to also be like starfish and are first embarrassed that we aren't and then horrified that we don't regenerate. (Cue Charlton Heston screaming Soylent Green is people or at the end of "Planet of the Apes" when they discover the Statue of Liberty.)
Writing stories under 1000 words is exceedingly difficult. Writing one of the five best (allegedly) SF short stories of the year in less than a thousand words? Highly unlikely.
So is "Asymmetrical Warfare" even a short story? Mostly - it has a story arc. The problem is that it's only got the one joke. I think comic writing is extremely difficult (and usually underrated by people nominating awards), but there needs to be something more to carry the story. Unfortunately, there isn't any more.