Interesting! None of the product I’ve gotten has what I’d call a strong banana aroma—or any strong aroma other than ethyl alcohol. (I got mine in 2018 and 2019, but I have no way of knowing when the respective contents were produced; the bottle was revised.) I do know what that isoamyl acetate smell is like. Testing my current sample neat and with water added, there’s an elusive sweet fruitiness in the nose that is detectable, but not strong; yes, it might be isoamyl acetate, but to my nose it’s either not sufficiently concentrated or it is something else or it is a combo.
As for what would be “authentic oke”, the more I read about, the less it seems like there’s anything to it other than any rough spirit (call it moonshine if you like) made in Hawaii. (Much like “Canadian whisky” isn’t much more definitive than any whisky produced in Canada.) Ti root isn’t apparently even a requirement—that just happens to be one of the readily fermentable materials that was available and popular at a time.
It would certainly be interesting to know exactly which products were in use in the 1930s-1960s at joints like the Halekulani. Then one could try to track down vintage specimens. But perhaps too much time has passed with too little surviving documentation and too few remaining specimens?