I'm pretty sure that's a "curation sniper".
Many people vote early on SC posts because they know @adm will upvote it eventually, which yields curation greater than their vote value.
Since the HF21, bots have been doing some "manual" curating or change their algorithm to cover the loss of sales.
Thanks for all the info. I wasn't aware that people could do this. I'm just trying to get my bearings so I can play this (steemit) game more efficiently.