hey there!
*spoilers for anyone who is stuck on the final boss*
So he has dialogue about being able to hear what the player is saying, when you press escape there are volume options. Turning the volume all the way down will stop the player yelling what they are swapping to as well as the music system. This makes him unable to swap to the correct stance and you can beat him. Had I more time I would have had a more direct prompt included after X time that explains what to do for those who are stuck, but maybe this was a bit too cryptic
Thanks for playing and the kind feedback and congrats for almost finishing!