It seems that you answered your own question? It seems like it's more based off Fiverr's side since what I think they do is just evaluate the sellers work and see how much the buyers are crediting them whether it's the buyers talking are mainly talking about how good the quality the work is or how fast they deliver with quality of course. And as of what @lloydsolutions said, "I think it means that gigs that Fiverr in all of their wisdom have deemed worthy" that's most likely what a Fiverr Choice gig is.
