Not necessarily. It would provide an attack vectore for sure, that being the data connection between profiles, but if it is implemented in a controllable manner (See qubes os), it's fine. The only issue I see with GrapheneOS in this scenario is: There is no uncompromised host for verification, so I don't really know myself how something safe could be implemented, however I would also think devs don't really want to, since there are ways which OP has already described some of.