Let's go another route. How about an aikido teacher who was around when Ueshiba was teaching who learned exercises that are either directly the same or extremely close to the same exercises Dan teaches? This teacher has never trained with Dan. Extremely gifted teacher, great person, and a treasure to learn from in the aikido world.
A second teacher (who doesn't teach aikido) who was around when Ueshiba taught. This teacher has aikido yudansha grading signed by Ueshiba. And this teacher stated that what Dan was doing was what Ueshiba did.
This is extremely valuable information. Who are these gentlemen?