Does a scientific instrumentalist not have to acknowledge other moral patients since they are not required to believe they exist?

If to a scientific instrumentalist, empirical models are just useful tools but don't need you to believe in them, then does the scientific instrumentalist need to believe in a moral obligation to others? We really only know other people exist empirically, especially the ones we are not currently observing. So is the instrumentalist not obligated to treat these other people as moral patients? It seems weird to have a moral obligation to entities you aren't supposed to believe in.