Well, in my Epirotean campaign, I can't recruit Illyrioi Thurephoroi/Thorakitai in Pella. Either you modded them in and forgot it, or it is a bug in my game.
I know that Chaonion Agema can be recruited in Epidamnos, sorry for not writing it clear. But I somehow have the idea of migration in mind, which would be a explaination for Molosson Agema and Chaonion Agema in Pella. If the Epirotean King is King of Makedonia, I think it's logical that a lot of Molosson would go there.