I wouldn’t read into that graphic at all — it was not meant to be any kind of representation of the frequency of these motions out there in the real world. It was just a listing of some players off the top of my head at the time.
Lots of bluegrass players appear to be “primary up” type players, like David Grier, Jake Workman, Bryan Sutton, Andy Wood, and Presley Barker, to name just a few.
In general, this is not something I’d worry about unless there’s a convention in the style of music you want to play. If there are signature phrases for your musical style like there are in bluegrass and Gypsy jazz, for example, by all means use the technique that gets those licks the way most people get them.