It could be a freak game, but yeah it's odd that an atrocious rebounder should grab 19 boards in one game. Speaking as someone who, back in the day when I actually played a lot of ball, was probably close to an "atrocious" rebounder (my eyesight isn't so good, my jump shot was solid since I didn't need to see the target when I shot, and rebounding requires good eyesight to go with the instincts), I know that even the worst of rebounders can get a ball to that bounces (and often rolls) away, sort of like the mutt getting the occasional crumb that falls away from the big dogs. Put me in the middle of the scrum, maybe I'll grab a live ball off the rim if it bounces away from the better rebounder and nobody else is attacking the rim, so that's how the rebounding stats go up for the atrocious rebounder playing more in the post, more opportunities for odd rebounds. But I know what it was like down there, the best I could usually do if I was in the post was to try to push my guy away from the rim so one of my teammates could get the rebound, or at least push my guy away and how the ball hits the floor where I stand a chance at collecting it. Granted, being the smallest guy on the court was as much a factor in my atrocious rebounding skills as the eye sight thing, but that just meant it took me longer to get the knack for rebounding. (Oddly enough, I'm a little bigger now but slower and with worse eye sight, and yet I'm a much better rebounder now than I ever was, which I attribute to experience and having a better sense of how the ball will come off the rim, even if I can't see the shot so well.) Anyway, the point is, either 19 rebounds was a freak game, or the other team had some serious rebounding issues that an atrocious rebounder could take advantage of. I'd like to see a link to that game, otherwise it's just all speculation.
Don't ask what sort of Chunks they are, you probably don't want to know. Blowing Chunks since Season 4!