Welcome to the forum!
This is actually the “correct” notation according to Gould’s Behind Bars. Of course, it’s totally possible to modify it, but not with Notation Options, as you’ve already discovered.
You can very easily achieve the notation you want locally, using force duration (o key, it’s a clamp tool on the left panel), either before input or after input. Since it’s already notated, select the note, press 5, o, 6 and you’re done. If you had not inputted it yet, simply press o before creating the note (to force duration to quarter), then don’t forget to disable force duration after that note if you want Dorico to “manage” note durations for you — it’s always good to benefit from Dorico’s internal rules to keep consistency, except in those rare occasions.
Hope this helps!