In case anyone was inclined to believe the above spin, the actual reason is that folks at seminars are asked not to discuss the material online in an attempt to keep it exclusive and monetizable. Most of the threads on this subject are marketing dressed up as discussion. Personally, I very much look forward to a frank discussion of training modalities instead.
If you have attended one of these seminars you know this is false; if you have heard this second-hand, the information is incorrect hearsay; if you have no direct experience, then you have no basis on which to make this claim. Speaking from personal experience, I was asked not to discuss the material because:
1. I am not competent to explain it.
2. A significant component of the curriculum is physical feedback that cannot be adequately expressed verbally or technically.
Of course, we do have copyright and patent protections for a reason. I wonder who would feel comfortable if someone was running around incorrectly explaining a methodology [you] designed. Since that poor reflection would ultimately be upon you. I express frustration here because either this kind of stuff is calculated to mislead readers, or it is prejudicial against those who train in it. Why not make the same claim when [your] organization's shihan teach a seminar. Clearly, the seminar is monetized and the instruction is proprietary to the instructor.
One problem you all seem to have is that you can't seem to separate the training methods from the application. We've established that aiki is numinous; it is not really a thing without a couple of different forces coming together, right? So what do you actually do when you wake up in the morning at the crack of dawn or when you begin your last three-hour solo training session at one in the morning?
Kuriowa Sensei used to talk about training that preceded kata, kihon waza. The best I can tell so far is IP is something that should always exist before waza (as a matter of being, to be more precise). In theory, if you are practicing aikido, you would be training IP with every technique or exercise. The problem is kata is often difficult enough - the idea of solo exercises is to provide a different environment in which to focus on a portion of the entire relationship between partners. In this sense, the training is similar to the simplification we have seen elsewhere; the removal of a second attack, the specification of kata, the speed at which we train. All of this solutions are designed to allow us to focus our efforts in learning.
And yes, it sucks to commit to training 4-5 hours daily. This is why IP is not for everyone. Standing naked in the bathroom waiting for the shower to heat up is now training time. Mirrors are not my friend. Or the spousal/familial training. There is nothing quite like the "you're an idiot" look from the wife when you ask her to push on your chest with slow, building pressure. Or the anxiety of asking a 4-year old to push daddy knowing that maybe you get a push, maybe you get a tiny fist in your crotch. Usually, a tiny fist in your crotch.