How does a fighter distinguish between more attacks because he as used action surge, and just having bad luck in combat or facing a better skilled opponent that can parry or dodge their attacks, or the other fighter actually being a bit better than him? Or do we assume action surge creates some special visual effect or sound effect like the bionic man running with his bionic legs, or things really happen turn-based in-universe, and for a few milliseconds every 6 seconds he can swing his sword exactly once, but another fighter swings it twice (sometimes)?