I know with the A, usually enemies that touch you will die. However, on this boss, it always seemed like touching the boss itself would kill one of the lasers instead. But this one time, it directly killed the boss. If it worked here, I'm sure it could work even much sooner?

I had encountered a bug similar to this about 15 years ago, but the boss ended up stuck in the flor while moving back and forth. Very cool to ACTUALLY see a video of something like it. I wonder if perhaps the A powerup actually does damage to enemies?