all the component which has tested and designed public api has it described in dev guide.
Unfortunatelly components which were designed in older version like 3.1.x could miss public clien side api. But as the 3.3.x branch is moved to stabilization only you could freely explore the client side methods of the components and use them as them not going to be changed.
The method which I suggested was not described as public because we not tested and documented js api during tabPanel creation (it was designed in very first 3.0.0).. but it could be found via fireBug and used.
We plan to correct this lack of tested and documented public methods in 4.x branch.