Yeah, I can see where your input is coming from. The boss was rushed (I only had an hour or so), and the relevance to the theme is explained in the description of the game.
But anyways (I'll explain it here), the theme correlates to opposites attract because it takes inspiration from Limbo. A game that was used as an example for this theme. Light and dark elements are the main gameplay mechanics (opposites) as you have to use light to traverse the dungeon. It was a bit of a more abstract approach, but I thought it would be a cool concept in execution.
Also, the gliding effect was made on purpose because it forces the player to be more cautious when moving. Thus making the game slightly harder.