First, thanks for the confirmation and hats off to VSO for preserving the original AC3 audio. Fantastic!!!
There are now BluRay files conataing 640 Kbps audio. CXD3 handles the video conversion with aplomb. However, one needs to separate the audio files and down-convert. I use an old copy of Soft Encode which I bought years ago. I then use DVD-Lab to remux the streams with a new menu added.
Maybe VSO and other experts here can suggest work arounds. Perhaps specific tools or a plug-in to down convert the audio.
Also, if you have a targeted DVD player that handles 640 Kbps audio on a standard DVD then there would be no need to convert anything.
I can give more information. I use DVD-Lab for authoring standard DVDs, and that program does not accept AC3 audio over 448 Kbps when compiling a standard DVD.