I tried them both. One worked for me; the other didn't, and I don't have unlimited training time left in my life. I really wanted mystical powers to be true, but that was not my experience. I had doubts about Aikido, too. Had I landed in a more esoteric style, I might be telling this story to a different group of people. But I found Yoshinkan Aikido to be practical and sensible. When asked about Ki, Kancho (Shioda Sensei) would often hold up his car or house key. This was our Founder.
I will keep saying that if there is compelling evidence to give IP a second shot, I will risk it. But based on what's available, it's a bad bet, IMO.
Maybe we can agree on this- I have found some mental constructs to be helpful. "Interrupting Uke's intention" for instance. If you want to call that IT, that's okay with me.
I was training in Yoshinkan, in Tokyo, when Shioda was alive - although he was quite old and we never had physical contact. Still, I think you might have found some unexpected dimensions to what he was doing - check out his associations with Kodo Horikawa.
In any case - I think that you're still asking for a higher bar for IP than for conventional Aikido. If trying it for yourself was enough for Yoshinkan then shouldn't that be enough for IP?
"Ueshiba sensei always spoke about the gods and the universe, things that nobody could understand, but I was finally able to understand what was behind it"
-Gozo Shioda, in the last years of his life