In the old days, Ueshiba did not accept anyone without any martial art background as students. If you look at the backgrounds of Mochizuki, Tomiki, Shioda, Shirata, Tohei, Akazawa, you will find that these gentlemen are/were competent martial artists even before joining Ueshiba. I believe the ranks handed out to them were based on their skill set rather than the time they put into training with him. There may be some exceptions which I am not aware of. Basically, we are looking at different set of standards - then & now.
Osensei didn't even name his art "Aikido" until he moved to Iwama, by which point plenty of local people started it with him as their first martial art. It was also around this time that the current minimum standards and the modern naming of techniques started getting developed. The Founder gave some people third dans within ten years with no martial arts background prior to Aikido. If only it was a just a matter of training for more time to get the same skills.