One more thing I’d like to add is that the assistant teachers encourage the student to effectively stop all vaci and kaya sankhara during the meditation itself through deep concentration, though Goenkaji does mention to “open one’s mind” to punna abhisankhara and “close one’s mind” in the presence of apunna abhisankhara (effectively describing anapanasati).
However, as far as the 10-day introductory course is concerned, there’s not much stress put on this kind anapanasati and instead, one should, I quote, “work with the body, not the mind,” therefore one should disregard ALL thoughts during the meditation itself and focus only on vedana, according to all the assistant teachers I met. One teacher put tremendous stress on this fact, and encouraged students to try to prolong this attention state where no vaci or kaya sankhara arises to as long as possible.
I was once told that vaci sankhara are products of sanya, which is not an object of the meditation, and should therefore disregard it as just another phenomena. This did not help me in the long run as I would often get frustrated with any mental chatter and found myself to try to stop it. Not good.