I'm willing to let that stand - I've yet to find any two people (in any aiki art or branch) who use the same definition for aiki, except when one quotes the other. Kondo (the senior one, I've forgotten his name) of Daito-ryu uses a very simple definition of aiki in one video. I doubt it's his only definition (it's quite simplistic) but it is how he defines the difference between Daito-ryu's Jujutsu and Aikijujutsu - it's mostly about timing. That Daito-ryu has a Jujutsu component (in other words, it is not purely internal, not purely aiki) is part of the reason they produced effective fighters. Most of the early proponents of Aikido had other training, so their Aikido training was likely focused (almost) entirely on aiki, because they already had access to the other tools.I think that we have different concepts of "aiki". If by "focusing purely on the aiki approach" you mean "focusing only on using momentum and/or the overcommitment of uke" I might agree with you. But that's not the aiki of daito-ryu, nor the aiki of traditional aikido.
Both those arts produced fearsome fighters while excluding muscular contraction from their training.
No, they really don't. They are playing soft in that video - nothing like they'd actually do in randori with someone like themselves. They bring no strength to bear that I can see. @Tony Dismukes and I have discussed this video before.They actually try to but can't. Muscular strength can be beat by clever use of physics.
Yes. I can do that, too. That doesn't work if someone also adds an off-angle movement. It's relatively easy to overcome tricks like that if you know them, and possible to stymie aiki if you know how it works (and sometimes even if you just understand movement and flow). Aiki is not magical - aiki technique is subject to the same limitations as most other technique, and can be overcome by a skilled opponent using all his tools (including strength, properly applied)