The fact that the sword deals multiple hits if left on an enemy is a bug. That’s not how it’s supposed to be played. The goal isn’t to wait for the enemy to be killed before moving to the next one. The idea is to throw your sword behind the enemy, then move to find an angle with a direct line to your sword so you can dash to it and immediately chain another attack.
You’re definitely not supposed to wait. After all, it’s a speedrun game! :)