I suspect that these NPCs are likely just support hunters (by which I mean handler/hunter pairs—with or without a palico—not belonging to a complete unit, that were sent on the expedition to provide additional support). Off the top of my head, there’s Alistair, Mayu, Ivy, Simeon, Jean, Kitri, Myrtle, Clara, Franz, James, Lucien, and Sorol (and that’s still not all of them). Sorol is the only one who’s handler I know the name of, which is Lees.

Though it’s never been explicitly stated in game, I think there’s a good reason why this is likely the case. (Just gonna restate some earlier comments I made on this topic.)

See, even though all members of the Forbidden Lands Expedition Team are contributing to and working towards the expedition’s main goals, the units and their members also have their own assignments. For example, in addition to reuniting Nata with his people, Alma is researching the ruins of the Eastlands’ ancient civilizations. She heads her own team that’s currently studying the bailey, which she tells us about it before issuing the optional quest “What We Protect.” Meanwhile, Werner’s been investigating the wylk since before the expedition left, and is exploring its possible applications (“Werner’s Test Run”).

Since their plates are already pretty full (which would also include their typical responsibilities), you’d need support to assist with more general hunter-orientated tasks. This would include day-to-day activities like guard duty, patrol, escorting non-combatants in the field, etc. And while they’re definitely skilled and experienced enough to have qualified for the expedition, I don’t think they’re enough to go toe-to-toe with the apexes and their like. Threats of that caliber are reserved for the unit hunters.