German commentaries can be expected for the final pool in Stuttgart aired on Sport1 - but they are underdogs against Olympic champions China, fourth best European team (and FIVB top ten team) Netherlands and the well doing young Turkish team of Guidetti at home (which is also in front of Germany in world ranking, despite only a bit).
So you're not getting German commentary on all the streams I'm watching from German sportdeutschland.tv? I guess about only half the games have English commentary and I've just been lucky it's covered all the Japanese matches. It's awfully nice of you folks to be broadcasting this tournament. And it's nice of FIVB to have hired a few English commentators. Not enough to cover all the matches.
I guess in the end, it's that if your national team is hosting and broadcasting on a local network, you'll have native language commentary. That makes sense. And it seems that a few countries are also broadcasting their team's matches for the whole tournament locally--China, Thailand, and I think Russia?--with native commentary. I'm a little slow on the uptake here, as an English only speaker without interest in Team USA and as a virgin to an international sport competition.