Here's my issue, though. If he is correct about the intended applications, then it means almost everybody is performing the kata wrong.
Grappling moves of the sort he shows in this video and others are very sensitive to nuances of body dynamics, angling, etc in order to be effective. I almost never see anybody performing the kata with the correct body mechanics to make those techniques work.
I started by learning Danzan Ryu Jujitsu first. Lots of grappling and throwing type stuff. I have since started studying Shotokan Karate and learning this type of kata. What I have found interesting is comparing what Funakoshi says about the application of the techniques in the kata, with what most modern karate folks say about the application of the techniques in kata. I believe that a lot got missed, left out and or altered along the way. But, I have found there is a lot remaining.
The more I learn the kata, the more I find. At first, I was seeing the punching and striking and blocking... and only believing half of it. Once I went back to Funakoshi's writings I started seeing escapes from grabs, and ways to off balance the other guy if he was grabbing me or if I were grabbing him. Then I started seeing where my jujitsu throws and sweeps would fit in, with certain escapes and off balancing moves creating the opening. Then, after working with a few karate instructors who had Abernathy like interpretations... I started to see how throws and take downs fit in. Now, changes have to be made to actually do the throw, like mentioned before. But, the foot movement, hip movement, power generation are very close... if you do it right. Once you associate this move from kata as matching this move from a throw, you can analyze where you need the power, and what those subtle changes are. Then when you do the kata, you can make those changes... create the power you need in the direction you need. Sure, you leave your hands "wrong" so sensei doesn't come over and correct you... but then most throws are more about structure, position, balance and hip action than they are about the hands anyway.
The thing to note is that I have not stopped practicing or studying my jujitsu. I still regularly practice the throws, locks, escapes... in jujitsu. However, I am able to see how the practice of kata has helped and improved my jujitsu, in very specific ways. Could I have made the same improvements in other ways? Possibly. Actually, probably. I have been studying jujitsu for almost 25 years and karate for 7-8 years. (and yes people have gone from white to black in the time I have and am spending at purple...) That means, that 16-17 years of jujitsu training failed to give me the things I have found through karate kata, that are in jujitsu. For whatever reason, perhaps I am just slow, I needed to look at things that way to get it. (when I show my jujitsu sensei what I learned about jujitsu, through karate, he answers: "yes... I have been showing you that since white belt...")
If the kata were intended to help with solo practice of these sorts of grappling movements, then they should be performed with the details and body mechanics which could make the techniques work. If they are just coded symbols with the movements which loosely approximate the positions of various grappling movements but with totally different dynamics, then I'd consider them to be worthless for that purpose.
Kata can be seen like a heavy punching bag. Having one and hitting it, is no guarantee that you are learning to punch correctly. In fact, without good instruction, left to your own devices, you are probably learning more bad habits and developing habits that will be hard to change later. You could even be injuring yourself, or training yourself to be wide open while delivering sub-par strikes that leave you way out of position afterwards... all because you don't know what you are supposed to be getting out of hitting the bag. How many threads do we have here, telling people not to go train themselves out of books and videos? Now, find the right instructor, that knows how to use the heavy bag correctly... and it is amazing how much he can teach you with that bag... punching, footwork, body movement, head movement, elbows, knees, clinching... the list is endless.
Just like the heavy bag alone won't teach you proper punching, kata alone won't teach you proper fighting techniques. But used correctly, by a good instructor, both can be used to teach a lot of different things. If your boxing teacher doesn't know how to use / teach the heavy bag... find a new boxing instructor. If your karate instructor does not know how to use / teach the kata (including the applications and meanings) find a new karate instructor... If you can get the same technical some other way, without the need of kata, do that instead.