I think it would be worthwhile noting that the baseline skills under discussion are basic body mechanics
which are common
to a number of SE Asian MAs. IMO, any discussion relating to principles, techniques, or tactics, i.e. irimi/tenkan, ki musubi, non-resistance, rotational dynamics etc. etc. is way off-base and is completely unproductive to the discussion. The reason being, these baseline skills are the basis for ALL techniques
(which embody THE principles) - and which enable irimi/tenkan, ki musubi, non-resistance etc. etc. etc. TO BE PERFORMED CORRECTLY.
To wit, part of this discussion will entail basic exercises
for people to get their "foot in the door" to these baseline skills. As such, it should be noted that these exercises are only for illustrative purposes. Once you understand the central concept of these exercises, ALL aikido (or for that matter, karate, jujitsu, taiji, yichuan, bagua etc. etc.) techniques can be viewed as an extension or application of these baseline skills.
BTW, Here's a much better video demo of bounce jin - I believe they are the same baseline skills currently under discussion, but far more sophisticated in usage than what would be considered "baseline" - for the purposes of this discussion.
PS: This thread made Brian Kagen's Pick for Jan 16th on AikidoJournal...