Setting aside actually using Meng Huo over Kirin for yourself or not, that it's showing up on friends lists is the interesting bit here.
Either one is savvy enough to know how to choose which eidolon would show up for a given element, and thus this is a conscious decision. Which leads to the question of why would you want to show Meng Huo over Kirin.
Or, one doesn't know how.

(also, said friend switched over to Medusa farming apparently, as the team I can see him using is light/St. Nick. So uh, the Meng Huo isn't being actively used?)