I think you have it backwards, actually - the jujutsu masters of the past DID have it - they just didn't call it aiki.
Aiki isn't something O Sensei or Sokaku Takeda invented, it was present in slightly different forms in many different arts. O Sensei's gift to us - and kind of a loaded gift, to be sure - was to create an art that took what was deep, inner, secret stuff in the ancestor arts, and plunk it down on the table on Day 1.
That was actually my point. They did have it, in one form or another and they didn't need to do it via "aiki". What Randall stated was:
"The secret to achieve "Ju" is through "Aiki"
This statement, to me, was more absolute. Like you said, it was presented in different forms in many different arts.