I always assumed that you couldn't acquire a morph or a nothlit because your mind was still technically in z-space, tethered to your current form. I'm pretty sure that's why a nothlit cannot regain the morphing power, because their mind would have to go through two or more minds while in z-space, and the complexity would block it or make it too complicated to compute. I'm pretty sure the Ellimist simply made hawk Tobias' natural form, as if he were never a nothlit, which is why he could now morph. Since hawk is his native form and not technically a nothlit morph, it would be akin to someone acquiring Jake or Cassie in human form.