I don't know whether a 256->256 re-encode would just strip out DRM without re-encoding the audio.

I don't know how the DRM works... it's possible that the DRM is somehow embedded into the audio data of the entire file and that the only way to strip it is to fully re-encode every frame?

And even if it *was* possible to just do a "strip" instead of a re-encode, it would depend on the software you were using to do the trick. Maybe the software isn't that smart and thinks you really meant to do a re-encode.