Re: Tai sabaki for reverse yokomenuchi
The kata form is simply called tanto soho. (FWIW there is a ken soho as well!).
I could not tell you for sure what is the date of its inseption. However, I will ask Parker sensei if he recalls how long it has been used. All I can say for sure is that the senshusei perform this kata every year at the All Japan Enbu. I saw it every year the 5 years that I was there.
In looking at my Yoshinkan publications I find nothing showing tanto soho. However, It is contained in a video tape that the IYAF put out through QUEST video in 1990 that lists the kata as part of the requirements for nidan and sandan.
I do not have the time right now to look through the complete "gijutsu zenshu" video series but I don't recall seeing it on those tapes as well. I could be wrong though and it could have been added to the newer box dvd set (which I don't have...I just have the old tapes)
I believe that it has been around for a while though.