Lots more than just lining up, or being accurate. The modern balls accompanied with the modern styles make most house bowlers too rev dominant,which inhibits their ability to play squarer through the heads.
Watch the best pros ( O' Neil, Barnes, even Rash and Belmo) They have learned how to use their ball speed and lower axis rotation to play straighter, even with their high rev rates. That is what the pros know that most good THS shooters do not. I do not disrespect guys who score high on house shots. They are skilled, and more accurate than people believe. What they usually lack is the versatility to square up and be comfortable, because they developed their game around swing area. Swing area is addictive. I remember as a kid even with rubber balls, I liked to hook the ball, and had a terrible time on fresh patterns