There is one thing we know the Okinawan seniors did a very good job not documenting their art. They did not want to share what they knew with us. I salute them in this.
Speculation about the past is fun but hardly will prove anything. Certainly if you possess actual documentation, or secondary level documentation (such as information from the Okinawan Karate Encyclopedia), or even better oral history directly from an Okinawan instructor a much sounder argument can be constructed.
Perhaps in the past some only did study a few forms, but as I look at the last hundred years many Okinawans took advantage of more studies and systems growing. I suspect fewer forms in the past were more part of less opportunity to train with others, especially in a walking environment of the past.
Shotokan is one of the most documented martial systems in the world, but even with those efforts we know so little. Were forms really modified? What does simplification mean?
More poignant to me because I came from the time nobody was doing any kata application studies and one of my seniors with training from Okinawa in 1972 refused to accept it was part of Isshinryus history.
On the other hand Shimabuku Tatsuo taught a set of responses to basic attacks, which of course did use kata techniques, but there was no bunkai study. My original instructor was a Marine in 59-62, my other instructor in the USAF trained there as a sho-dan for a year in what was then an almost entirely Okinawan dojo (the Marines then had their own dojo on Camp Foster).
In fact Kyan only taught kata and did not teach applications (there was no Okinawan term for bunkai).
Likewise Kyans students who became instructors followed much the same pattern, just kata. That does not imply students didnt work on specific application techniques, but that the complete analysis of kata potential was not the art. (from several friends in different Kyan based systems of study from their own studies on Okinawa).
So its not impossible that the Itosu lineage was not different. Bunkai was first used by Mabuni in his first book to explain to the Japanese what kata technique might be used for. Shiroma Shimpan in Nakasones 1938 Karate-do Taikan showed how to use techniques (most frequently adding other movements or perhaps Demuras description of Kakushite Hidden Hand. Likewise in 1933 Mutsu (originally a Funakoshi student) wrote Kempo Karate and shared a ton of technique applications (1/2 of the book) but didnt tie them to the kata. In 1930 he traveled to Okinawa to obtain more knowledge.
So its not an impossible concept that Funakoshi did not share what he was never taught.
As for taking an art he had studied one on one, and turning it to large group instruction, changes may have been made to fit the new model. Harry Cooks book Shotokan a Precise History contains suggestions about that.
Funny thing even a few words from Funakoshi Ginchin cannot really explain what his part of the process of change really was. We only truly know it just happened.
The past is done, the reasons not clearly explained just are.
Funakoshis idea of having karate move into the schools really didnt happen exactly that way. In fact in modern Japan very few people really study the martial arts.
There is a problem trying to cover too much ground and I apologize if Ive made any of this more complex.
But to clarify, I practice Isshinryu (on days Im not practicing a wide range of other arts. I was a system extensively modified by its founder (and in truth simplified) and long ago I struggled to understand how it could be used. On my way I started also training with Tristan Sutrisno and his fathers Shotokan and learned a little of his extensive bunkai entirely of the kakushite variety.
His sharing among other studies led me to my own analysis of Isshinryus 8 kata, and then meeting and training with the late Sherman Hariill until his death. Only a few short hours but in that time he shared 800 technique applications for Isshinryus 8 kata, and on my own Ive worked out one or two more.
Thats why I look at Shotokan kata (and not using the Sutrisno model) find hundreds of ways to drop someone with them, who cares what was taken out, theres more than enough there for anyone. But I dont spend my time with Shotokan studies for the most part
Sherman used to say Push comes to Shove Id just punch but he spent decades on the makiwara and him and his students dropping each other with hard precise strikes. He only use one striking point, your body and worked so any strike drops one.. truly
His students still follow that path.
I dont exactly do the same but one punch should be enough, but the question isnt one punch ,but were you strike with it, such as dropping to your knee and striking into their foot to break it, or striking into their hip joint, or striking from the side into their thigh to drop them or into their arm, etc.
Well I dont want to ramble.
You might check out my blog for some of my current research too:
http://isshin-concentration.blogspot.com/
Specific ally these articles:
April
Itosu Anko A New Direction for Toudi
May
Itosus Reflections
The Game is Afoot Watson
Watson Look for the smallest details
It is not BUNK I say Watson