The aikido curriculum was dumbed down and made the way it is today simply because 99% of Aikido practicioners would probably drop out. My guess is he just wanted to spread Aikido as something that everyone could practice, and didnt care whether or not the "essence" got transmited. Otherwise I think you'd see much more information on the way he trained in private
I'm still thinking over what Ueshiba did during his "teaching" years, whether he really cared to spread the knowledge or not. But I do think that his son, Kisshomaru, was the one responsible for starting Aikido along the technique driven path.
Ueshiba is known for a few comments in his later years, such as:
That's not my Aikido
and upon seeing people doing "soft" aikido, asking them what they're doing since it took him twenty years of doing hard stuff before he could get to the soft stuff.