How are you defining temporal death?Lane,
Have you consulted Vos? In Vol. 3 (Christology) of Reformed Dogmatics, Vos notes that “the concept of death includes...Separation of the source of life for the body, because the soul can no longer retain in its organic connection. This was also the case with Christ.”
He goes on to note that “If the concept of death is separation, dissolution, then this characteristic must come to light in the strongest possible way. Hence the soul and body must be torn apart.”
In the context of eternal death relative to temporal death, Vos compares and contrasts Christ with the lost. Both suffer both types of death, whereas only the elect suffer only temporal death. Regarding the lost, Vos speaks of soul and body being reunited (which presupposes a severed union) upon the temporal death [the intermediate state] giving way to the fullest expression of eternal death in the reunited body and soul. He also observes the order of things. Christ suffered eternal death, then temporal death. The lost experience the same two but in reverse order. In both cases, only in eternal death does the body soul composite remain intact.
Any appeal to mystical union of believers’ bodies dying in union with Christ has no relevant bearing on the anthropological subject at hand because although the bodies of believers die in Christ, the bodies of the lost don’t. Therefore, any appeal to mystical union of body and soul, if it’s to make a point about how body and soul relate to personhood, must apply to all humanity in the intermediate state. It must apply to quick and the dead. It must transcend union with Christ.