Re: Where does "Morote Dori" come from?
Saito Sensei always made the point that uke's holding / grabbing techniques were all based on controlling nage; not letting nage be able to use the hand / hands to launch an atemi against the attacker. When holding kata dori uke should be able to block a punch from nage (from either hand). Morote dori (also called Ryote mochi) was shown as a technique to control nage - uke should be using the two-handed grip to control nage's elbow and thereby keeping nage "at bay." Sensei also sometimes explained that the original Morote Dori called for uke to start by striking ("calling out") nage's hand by way of extending tegatana towards nage's face, starting from the position of the leading hand placed down by the forward hip and leading straight up the centerline to nage's face. This is, by the way, the kihon form that is taught in the Iwama lineage for Shomen Uchi ( in this case it is nage that initiates the "from below to above / towards the face" tegatana / atemi). Sensei would use the Kuden "Aite no ki wo yobidasu" - to call out the opponent's ki.
But I digress :-)
Morote dori was taught very often in Iwama by Saito Sensei, as well as at many of his seminars, always with the focus being on using the hold to control nage - using the slight twist / turn of nage's arm to lock the elbow. We were taught to call out the Morote Dori grip by extending our forearm towards uke with the little finger towards uke (our thumb towards ourself), thereby setting up the proper control grip for uke.
In regard to O-Sensei's use of Morote dori - I would have to say that Saito Sensei would not put as much emphasis on this holding technique as he did unless O-Sensei also taught it extensively.
I hope this can clarify things to some extent.