Presumably both the 24 and 48 fps versions were shot with the same cameras, with the 48 fps raw being mixed down to 24. Why would that affect sensitivity? Sho

Presumably both the 24 and 48 fps versions were shot with the same cameras, with the 48 fps raw being mixed down to 24. Why would that affect sensitivity? Shouldn't both versions be equally sensitive? If not, couldn't this effect be compensated for in post?