Guy in the coffin aside, it's not just about the "rule" and story progression of the ride, it's also about the ride's impression on and ability to surprise first-time riders.
Up through Madame Leota, if you're a first time rider, sure, it's neat, but you haven't really seen anything that a small time amusement park haunted house couldn't do. Then BAM - smash cut to the jaw dropping MASSIVE SCALE ballroom scene, loaded with ghost animatronics that actually appear to be both physically in the ballroom AND transparent.
When the ride was new, something like that was unheard of. Even today, if somebody knows nothing about the ride other than it's old and considered a classic, the ballroom scene still has a huge wow factor as it still looks better than most scenes you will see in modern rides. So having a confirmation before this scene that yes, there are full-bodied ghost animatronics in this ride, is a bit of a big spoiler.
Pirates of the Caribbean does the same thing where the drop transitions you from quaint scenes of caves and skeletons to being in the middle of a battle on a shoreline.