This was deguchi's, personal view of how we should develop ourselves, and indeed this was his own interpretation of the beginnings of the kojiki.
Spirit first,Second Power, Third Body. Interestingly the three deities mentioned above are the first deities described at the very begining of the kojiki.
This information has been around a very long time.
1In the beginning God created the heaven and the earth.
2And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.
3And God said, Let there be light: and there was light.
4And God saw the light, that it was good: and God divided the light from the darkness.
5And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
6And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters.
7And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so.
But whether one views such spiritual teachings as instructional or merely mythological does rather depend on one's religious beliefs, doesn't it? Do you mean to argue that one must adhere to Omoto-kyo in order to draw spiritual benefits from aikido?