The situation is a little more complicated than just needing to hide emotions. From my understanding, Emil... had a lot to adapt to. Surely, if he were Ratatosk the entire time, he wouldn't have been able to make any of the connections that he has. It's more of a survival mechanism. Whether this happened willingly or unwillingly... it is unlikely that he remembers, and surely would not accept the ideas if we presented them to him.