Sure, but his rebounding rates improved in what was seen on that short trip, not just his overall rebounding which is a product of his increased playing time. I don't have the exact number on the top of my head but it was a decent improvement in rebounds per minute. Some people were giving Black crap for the games he played this year, and making it seem like his quality of play was due to a plateau of skill, and not due his injury. I don't blame people being cautiously optimistic though, I just think that there are safe assumptions to make based on that trip, and based on feedback that I heard from people that actually were there (including that his defense improved significantly but I'm taking that with a grain of salt as well).
Even if he doesn't improve with fouling, 15-20 minutes per game may be all he needs to make a big impact due to our projected depth at the position. Having him improve in those areas definitely helps our ceiling though.