For adding a single method, it does make sense, changing the active source file to edit the body of the generated function.

If adding multiple functions, it may also make sense, stay in the declaration and continue refactoring. In the case where multiple editors (splitview) are active, it makes even more sense, not to change the current source file on refactoring.

May be, its worth to create a refactoring method "generate all missing definitions". But please: with the option of not changing the active source file.