When I create a non-pitched cue over a normally down-stemmed note, the main note’s stem flips up. Of course I can re-flip it manually, but it’s an extra step that looks like a (minor, to be sure) bug or unintended consequence to me. Why was this flip felt to be desirable?
…and if you redefine the main up-stem voice as a down-stem voice (Edit > Voices > Default Stems Down) then all notes in that voice under the cue will have their stems pointing down.
That would suggest to me that Dorico’s doing the usual thing it would do when two voices are present on a staff. To put that another way, I suspect Dorico doesn’t know to do anything different if one of those two voices happens to be a rhythmic voice off the top of the staff.
Interesting. It’s easy to handle with an F to flip the individual note, of course.