Your are right. But the question to me is: Is it easier for the user to move the things that are out of place after the file has been imported to their correct position or is it easier to re-input all of them?
My preference would be to get things Dorico doesn’t understand into Dorico and then move them around - or delete them, if I want to.
You gave the example of text that is attached to the page. Of course, since Dorico does a better job in engraving my music, those items will most probably sit in a wrong spot at first. But I already know this will happen when I import MusicXML into Dorico. Music will be respaced, and text that was sitting in between 2 staves before will need to be moved to wherever it may belong then. But that’s ok for me.
Maybe we could get something in between: A simple option “Would you like to import unknown things as text or skip them?” on import might lead in the right direction. Later on the team might come up with more sophisticated solutions.