Thank you for your comment!
You analyzed the game pretty well. There were some ideas behind making some of these things intentional, like making the boss only do different attacks when it gets at half hp (like a second phase of the fight) but it indeed lack of some explanations, that maybe if it was a little more polished should be just intuitive.
I just notice some of these things right at the end/after finished the game due to lack of gameplay/beta testing. So by making comments like this I can understand better the things I did wrong and maybe improve the game after the Jam ends.