It is a bit hit or miss in my experience. If the commentary is available on the computer or iPhone, I persist with it. I refresh the app and sometimes that helps. The World Feed is usually the one with the commentary. It is frustrating - hopefully they will improve the app in time. I think they have only a limited number of people to do it.
However I do think that early in tournaments when there are so many games being played at the same time, only the main courts will have commentaries.