I will be the negative nancy here and say the animation in the actual flashback was much better in the actual anime. But the short film itself is super sweet!
You're pobably mixing animation with character art because there's no way you saw this short and thought that the anime had better animation.
This Law remake is brilliant on every level. Just the first cut alone, the ambient lighting, the white/black contrast, the highly expressionistic drawings of Giolla and Machvise… its such a strong opening and seems to reflect Law's nihilistic viewpoint, unstable emotional state and disconnection with his surroundings/reality.
Despite the minimalistic lineart and shading, the shapes of the drawings are clearly defined and purposeful, giving the characters a palpable sense of three-dimesionality and weight. The animation and shot composition are framed, timed and paced to perfection.