Not quite Marc
The senior taught in the role of uke and that was primarily in weapons based kata - not necessarily in jujutsu techniques. It would be a mistake to thing that these seniors were the level of kyu grades or early dan.
That said - I know in systems which are kata based the role and expectations of uke are taught from the beginning. Learning that helps you to understand the techniques from tori's point of view also. In Shodokan for example it is expected that you should be able to effectively teach techniques required two kyu levels below your own.
I do agree with your point though - with the proviso is that they teacher and others should be all on the same page.
We are both referring primarily to koryu. The weapons-based kata had/have a continuum to hand-to-weapons, to hand-to-hand based upon an particular "operating system." The distinction is more an artifact of the operating system in use with tools. There were no kyu grades or dan grades for that matter. Our waza is a form of kata as well. I think that we are essentially in agreement. I think that you would agree that a beginner's body is a good feedback mechanism for how our waza works in people who have not been "taught" how to respond to what we do. Likewise, "playing" with friends from other martial arts is typically very informative to all parties as well.