Well you're absolutely right that the piano score should divide left and right hand. But the application is not almighty and it is not the replacement for musicians' aural skills. the main intention is to ease the process of transfering the idea into piano score. So as I see it, if you wanted to write your own composition into piano score, you could for instance play at first one hand alone and generate the MIDI output, then the other hand alone and generate thi MIDI output, then you cna mix it in the appropriate software. In this way you would be able to create a piano score much faster in comparison to manal writing in any software.
What do you think about this point of view?