While Dorico supports rotating the hairpins, when will it correctly adjust the ends so that both end points are horizontally alligned?
No, Dorico won’t do what your picture suggests. It rotates the hairpin as a path, which is (as far as I’m aware) the conventional way this is done in published music.
Verdi- Don Carlos, Ricordi edition
Act II 7 measures before letter H Page 99g
Act III N.8- Scena Duetto e Terzetto, page 288 strings. Saw it in a bunch of other places.
Pretty sure I saw this convention in a bunch of other places as well.
I’ve seen these too - rare but elegant!