Thanks for your replies!
high5ths, when I last used Dorico, the “Determine by context” option was the one of choice to get beamed groups of notes right - “default direction” often was wrong with these groups. On the other hand, groups of notes without beams and middle line notes always include middle line notes in the context with the “determine by context” option. There should be an additional option which stems notes by context when they are beamed and leaves middle line notes alone in groups without beams, which I mean is stemmed down.
This is not related to “traditional computer rules”, but to - as you call them - old-school manual engravers rules since the beginning of the second third of the twentieth century. Only manual engravers in the nineteenth century would sometimes - not always - stem the middle line note up depending on the context. This is what I, for one, found in hundreds of scores during my professional conducting years…