Chapter 609 Build-A-Body Part 1
"Well, before you go too far, just note that every part of your basic humanoid body will be improved, but we can't go too far. We can actually push your Memphis body further, it's one of the reasons you'll be stuck in that form at first. That form will essentially drag your humanoid body up to acceptable levels.
"One of the little tricks we're using is for your soul to think of your Memphis body as a transformation, match it, then force the link to your new humanoid form instead of your old one. The fact that you couldn't actually go back to your old body is something we'll be… obfuscating from your soul, if that makes sense.