I do not know how you arrive at the conclusion that after O Senseis passing training in Jo/Ken , Batto Ho,suburi , kumi tachi, tachidori /jo dori went out the window.As a member of Birankai International I can safely say all of these disciplines[including Za Zen ]are practiced consistently within our group.
Why not take the time and effort to look at Biran online and see for yourself?Or contact me in Pm.and I can give you futher info.
I have had the good fortune to have trained with Chiba Sensei on a number of occasions... He even had me teach a class once at one of his instructor seminars. In fact, technically, as far as hombu dojo was concerend, my San Dan went through him (although I had another certificate from my teacher Saotome Sensei). Anyway, I have worked with Chiba Sensei, Imaizumi Sensei and Saotome Sensei, all deshi at roughly the same period at hombu. All three have fully developed weapons training programs. What is interesting is that they are not for the most part terribly similar which leads me to believe that they received training from an outside source and then were allowed to run with that training and largely work things out for themselves. It is also clear that some of the deshi from that time didn't not get such training which has lead me to believe that it was optional and some folks took advantage and others did not. Anyway, I always learned a lot from Chiba Sensei's weapons work. It was hugely powerful which I loved.