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.
The concept of "Aiki" is not limited to our Aikido techniques alone.
"Aiki" is present in any technique that allows a person to experience "Ju" with an attack.
For example: If your opponent pushes you, & you use his forward force/momentum (together with a little of your own force) to break his balance, you are actually using "Aiki" to experience "Ju" for yourself.
If a person truly wishes to experience "Ju" in his techniques, he has to use "Aiki".
"Ju" & "Aiki" are very closely inter-related. Their relationship is that of a "Cause&Effect" nature.
The use of "Aiki" allows you to experience "Ju".