The model of music notation in Dorico is completely different to the data model in Cubase and the audio engine. There is a many-to-many mapping between a notated note and a played-back note, and maintaining that relationship so that you can perfect round-tripping between Dorico and Cubase is incredibly difficult. And it probably isn’t what most users actually want. There are about 10 phases of processing in Dorico that are required to turn a note in the score into the (possibly) multiple events required to play it.
We anticipate that integration between Dorico and Cubase will improve over time, however we don’t know yet exactly what form that will take.