So, even if I acknowledge how useful a free hand can be - and I do - as I said, one can in about all normal situations pretty easily get a free hand. There are many martial arts styles that train, though, with two weapons in hands and are based on that. Eskrima for example does so in many training systems. In kenjutsu nitojutsu (the use of both swords) is a not uncommon - not only in Hyōhō Niten Ichi-ryū which was, I'm sure you know, founded by Musashi, but also in other kenjutsu schools.
It's not because he was the best samurai 'evah' that he could do it and be successful with it - that was because he received proper training - but rather he was reputed to be one of the, if not the best kenshi of his time, at least, because he made extensive use of these techniques.
Two weapon fighting styles aren't simply aesthetically pleasing, but they are also quite deadly, especially if employed by a skilled practitioner. Also, there is no "both hands holding weapons at all times" doctrine in Ogunoke, rather it "is based around the use of one or two knives". I really don't see how a "both hands holding weapons at all times" doctrine flows from that. It sounds more like a "use two weapons when appropriate, when one is appropriate, use one" doctrine.