Ehh… the guy’s argument for 64-bit mixing is fine, but the end result is still going to be 24-bit or less depending on the plug-ins and such used in the mix.
Until there’s some revolution in audio recording that makes microphones as they are now obsolete, a 24-bit file is biggest you’ll ever need for a recording to have pristine quality. So if your stems or mixdown are higher than 24-bit, you’re just wasting space on your hard drive.