Morihei was pretty rigorous about Asagao, if you watch the old films and pictures. Kisshomaru was too, as far as I recall, although I don't remember him ever mentioning it specifically. Sometimes Kisshomaru would mention "te-gatana" - but people seem to interpret that differently than Asagao.
Saito used to complain about how "some people" held their hands, IIRC.
The background image on www.aikidosangenkai.org
is actually a photo of a kimono fabric with....an Asagao pattern.
What I thought was interesting was the difference: Keeping the hands straight vs. the "slight rotation". Am I right in thinking that while Takeda and Osensei emphasised the "te-no-kaeshi",
Sagawa changed it to keeping the hands straight? I notice Akuzawa Sensei
of the Aunkai also keeps the hands straight. I haven't found any videos of other IP/Aiki exponents doing the exercise to compare, but it seems that even te sabaki
can be viewed as "waza".
In other words, could stripping it down be a way of going for "raw" kokyu-ryoku
outside of the method of deployment?
NB: Suwari Kokyu-Ho
is one of only two "techniques" that Osensei didn't seem to mind having written down in a list of rules as something that should be done in daily practice.