Re: Origin of ushiro ryote and ryokata dori
Notwithstanding claims that Aikido is a different system than Daito Ryu, I get a historical context that says aikido attacks and waza have a strong relationship to Daito Ryu. But you also have some context that implies Ueshiba was moving away from Daito Ryu, largely due to strong input from his student base to develop what we call the "waza" that emerged. I can't say I am surprised some techniques were left behind, or some components emphasized over others.
That said, if our instruction is based on a lowest denominator, I am not sure teaching someone to defend a strong rear attack has value if they can't defend against a rather bland grab to begin with. If I was lifting weights to get stronger, what would be accomplished by me failing move an inappropriately heavy weight? Injury? Confirmation that the weight was definitely too heavy? I know plenty of aikido people who struggle to manage simple attacks - I am not sure what would be gained by implementing a stronger attack. I see this as a walk before running thing.