Basically, the ego chooses its dominant function, and dominant orientation, which then become paired into an "Xy" "function-attitude".The other three functions and opposite orientation are initially rejected into the unconscious. Hence, an auxiliary, tertiary and inferior function all in the opposite attitude. However, the Puer ("eternal child") complex orients the tertiary function into the dominant attitude to maintain the ego's dominant orientation.
Hence, when the functions differentiate, we end up with this alternation of attitudes in the functions. (Of course, the opposite of these, including the original tertiary in the opposite attitude, end up in the shadows).
Thanks for your thoughts. The more I think about the word "healthy" as it relates to psychiatry, the more I question it. Same as I question attempts to reduce the human mind into any specific linear form of processes.