The isolated score can't really be said to be 'incorrect', because its aim was to reproduce the music as originally composed by John Williams, not the edited version that is actually heard in the film itself.

There are numerous differences, mainly in terms of things having been left out of the final cut so that certain scenes would be unscored, even though Williams had initially written music for them. It's actually quite a lot of fun to watch Empire with the full score running in synch.