Going into our Switch 2 testing, we'd received no real indication from Nintendo on whether back-compat would actually be any faster than running the game on original hardware. Wii titles didn't run any better on Wii U, for example. However, Switch 2 is different. It's not using full hardware backwards compatibility as such - it's effectively using a translation layer to run the original game code on the new system. In this scenario, it would probably be a lot harder to limit games to original performance levels as opposed to just letting the new system run those titles with whatever system resources the Switch 2 can throw at them.
The end result is that - remarkably - Batman: Arkham Knight is as fixed as it can be on Switch 2 without going back to the game and optimising it. While the game still possesses ugly pared back textures and hideous aliasing problems, it runs as flawlessly as it's possible with the original code. Extra CPU and GPU power in combination with the faster storage are effectively brute-forcing the game to be everything it can possibly be, given the design constraints placed on the original code. Is it perfect? Well, in Batmobile driving, while frame-rate is fixed, animation error hoves into view, so despite a locked 30fps, something still doesn't look right.