They sort of are speaking in code, Emma asked Magneto to buy an Island from Namor to use the space to build a place for the event, Magneto and Emma used to be partners on the Hellfire Club so they are used to do events like this to interact with different socio-political representatives of the world and Namor was someone they have been trying to reach out since PoX/HoX so it makes sense to involve him in a diplomatic event.
This event is giving me vibes from Hickman´s FF run, from where they invited their foes to develop a strategy to defeat "AU Reed Richards" so I expect some suprises of that kind knowning Hickman and Duggan.