My guess is that the Dubois Manhattan recipe is probably adapted/modernized from the slightly retrograde but well-distributed 1887 JT:
He omits the Curaçoa, Maraschino and gum syrup references because they’re anachronisms—why wouldn’t you omit them? The Boker’s reference remains, making a New York publication the likely (but not guaranteed) source.
Another possibility is the entire Dubois recipe is an interpolation from no single source, although that 1/3:2/3 proportion is a little uncommon, and again, Boker’s.