I have never seen that photo!
I don't think that you can see any particular tendon development. I don't even think Morihei's legs look that big at the time. But, great find nonetheless.
Do you see what you were looking for? Why or why not? What do you take away from this?
He looks quite old, by the way. How long before his death was this taken?
The photograph was taken in the new Hombu Dojo, which was opened in 1968, which is one year before Morihei Ueshiba passed away.