I also believe it is done on purpose; which makes sense. The idea of course that the hero is a "player" which learns, adapts and improves, while you are strong, but you have no margin for growth, you are on a fixed move set, you are supposed to always replicate the same pattern with the same speed.
I don't any doubt that, but it just kind of ends up making the gameplay a little too clunky for me when it comes down to the actual "playing of the fight".
The game achieves what it wants to achieve, while the hero gets better you kind of just stay the same, which eventually is not enough anymore... the concept is great; it's just kind of a little boring to actually play.