To clarify, my tailor did mention he usually does the knuckle thing, but shortened my jacket specifically because of my short torso. Then again another tailor cut it following and I felt both look fine; they probably also took into account other factors in their house style when determining the best jacket length too.I think torso:leg ratio comes into play as a secondary observation, no? Typically (or at least what I have always experienced and seen in other bespoke garments is you measure your jacket to your thumb’s knuckle - which means you are measuring torso:arm ratio really, no? From there, some people prefer it a tad shorter (a trend that most people dressing footballers seem to have adopted) or longer (Sexton style). I’m 5’9” and jackets that are shorter than my knuckle just feel oddly childish.
I do have a few that are cut longer, always depending on how “deep” the waist suppression on the coat is, ie if there’s a clear supression subtly starting below the armpit, then I see a longer jacket as more elegant and forgiving. A jacket with a more brusque waist supression (just at waist level) tends to look a bit ridiculous if too long. So maybe there’s also the ratio of the two overlapping triangles?
Agree that deep waist suppression looks better with longer jacket. I think it is also the case with very low lapel rolls and open quarters. The curves look too abrupt and draw too much attention on shorter jackets in my eyes. Would look like you're wearing a mini skirt.