What makes it so special?
Jumpluff is in NU, Smogon just has an Uber tab for it because it is viable in Ubers as a Sun Staller, using things like leech Seed, Encore, Sleep Powder, Toxic, Protect, Substitute, and Chlorphyll to become a fast and effective staller.
It is in the NU tier. But its speed reaching 700 in the sun is insane. And only outsped by Deoxys -S with a scarf. I has both Encore and Leech Seed. Plus SleepPowder, Toxic and Substitue are amazing in the Uber tier. So it is kinda unmatched in the Uber tier as a status spreader.