Because of the way the blu-ray format was designed, films that run at non-standard frame rates (not 24, 25, or 30) have to be interlaced for blu-ray. This is the reason that many silent films are 1080i instead of 1080p. There is nothing wrong with interlacing if it is done properly for the right...
Steamboat Bill Jr is the disappointment in this set. The DVD wasn't as washed out and it had a much better score. Sherlock Jr is the opposite. The bluray is vastly superior to the DVD, which had a hideous score.