That's a good argument, but there could be other reasons why nobody has publicly come forward with a negative opinion. In the public sphere, Dan has a history of being somewhat aggressive in the face of criticism. Most people would rather not get dragged into a public conflict.
To clarify, I'm certainly not arguing that IP/IS is BS. I'm simply pointing out that I don't feel convinced based on what I've read on the Internet (absent of direct experience, admittedly) that it is the holy grail of martial arts and the missing component in 99% of the world of aikido. The rhetoric around it has been pretty hot and heavy.
That's a pretty small and personal claim to make, in my opinion. I don't think any rational human would begrudge me the right to apply the usual critical thinking skills. Once you give that up, things get cultish pretty quickly.
Don't give it up, just don't try to assume it's bunkum either.
My suggestion would be to take an opportunity to train with Dan or someone teaching the sort of skills being discussed if you get the chance.