To be absolutely direct and clear, I do not believe empty force is in any way what O'Sensei was doing, and people who peddle it - regardless of what they claim to be doing - are at best charlatans, and at worst actually believe in it themselves. That does not mean you can't cause an opponent to react before contact based on what you do, but there are sane limits to this and empty force sorts of things (endemic unfortunately to most of the ki/chi arts) are definitely outside of those sane limits. I interpreted your posting of the original link to it as some sort of unfortunate (mis-)interpretation of what I was saying earlier.
The reason I posted those Shioda videos is because he illustrated the point I was trying to make earlier, that there is an underlying quality to what he is doing that goes hidden in the techniques, but is visible (and unfortunately a bit too palpable to the uke in the last one) in those particular choice moments. Without that quality, he may as well just be flapping his arms around and people in an effort to reproduce it come up with stuff like, uh, empty force as some sort of misguided interpretation of what he was doing. There is a difference between an uke trying to get out of the way of what he knows to be truly an oncoming freight train vs. collusive movement designed to make a paper tiger look better.