I'm pretty sure it's not working as expected right now, so it's useful.
Let's admit the mission affinity is Arcanist and Hyur. The party should have both an Arcanist and a Hyur (or an Arcanist Hyur) for the chemistry to be activated, or the Hyurs (for example) will have the chemistry activated no matter if there are Arcanists or not? In other words, should all the affinities be matched or just one for the character with the chemistry?
Right now it's something like "when the 3 mission affinities exist", but it's bugged anyway.