In his Notation book, Gardner Read makes the fair point that tuplets with square brackets should stem from the side of the head of the first note in the group. - This is because the bracket (used when beams are not there to do the same job), resembles and so could be construed as a beam.
Thus:
Wrong tuplet placement:
Correct tuplet placement:
The manual does not indicate this, though I found…
…Can Dorico be set to place tuplets correctly by default?
As far as I know, the default setting “always at the note head side, when there are no beams” unfortunately does not exist. I was also trained in such a way, that triplets are not placed at the neck side in this circumstance. Off course there are exceptions there …