That is kind of a major point both IRL and in Baki.
Mushahi, the real one, considered a duel to have begun the second it was decided you two would fight. Anything and everything was on the table, every moment should be in preparation, any tactical advantage should be leveraged, because it was you or them and as a warrior it is your job to make sure it’s them who falls. Doesn’t matter how you go about it, winning is winning and when losing means death you better fucking win.
Honor, respect, bushido (a very misunderstood topic these days), those aren’t just things that can get you killed but those things can be used against your opponent to kill them.
Both Five Rings and Dokkodo are magnificent works, ones I have read many times, but they aren’t gospel and you have to understand the time they were written and the man who wrote them to really appreciate what they mean, and even then I don’t believe it’s possible to know the exact meaning Mushashi had in mind because it’s truly alien to everything we know in the modern West.