Weak cover on a low flaring core can make for some very skid snappy ball motion, but say you need a slow smooth ball motion, but not much overall hook, think urethane.... but stronger. This may have been a weak enough cover, but needed to manipulate the core dynamics more than usual to get it to flare enough to work.
And if that is Rash's ball (finger holes seem to look like it), it wouldnt surprise me to see them trying some odd layouts the way he has been bowling this week.
Bowling balls seem to usually pair strong covers with high diffs, and weak covers with weak diffs, and that usually gives you a pretty spread out range of reactions, but sometimes it can help to use a flare reducing layout on a strong core ball, or in this case, a flare increasing layout on a weak cored ball.