Then let's pretend/agree that IP exists- just for the purpose of this discussion- and dig into "why".
Is it practical? How does it help me fight bad guys? And for the record- that is all I care about.
If it exists, then when you had to put hands on the bad guys, you can obtain the results you need with less strain on your muscles and soft tissue.
Where I fit into the whole argument is that I don't think the training methods these folks use have any relation to what Ueshiba and Takeda or any of their students except Sagawa did. This may not matter to you given where you are coming from.
The drawback is the IP training methods apparently take a lot of time and effort, though it seems like it sucks you in when you start doing it.