In the end of the G1 Marvel Comics, Optimus Prime was human. And if I recall correctly, the transforming truck robot was not alive and was rebuilt by Primus. And even when the Powermaster body was built the first time and Optimus’ consciousness was transferred into it initially from the computer disk, it was not viable. Optimus was dying, so that’s why the nebulan human had to be added, melded so that Optimus Prime could live. So Optimus and the nebulan became one and the same. Optimus had essentially become human and his transforming truck robot became just a Pretender shell, not alive.