DVd-Audio authoring is not required. Two channel 24bit linear pcm is permittable in the DVD_Video spec.
while the DVD-Video spec allows for 24 bit LPCM, it must be sampled at either 48 kHz or 96 kHz. The DVD-Audio specification allows for 24 bit LPCM at 44.1, 48, 88.2, 96, 176.4, and 192 kHz.
Based on that, if the original material is 24/48 or 24/96, then either the DVD-Video spec or the DVD-Audio spec will work. If the material is something other than 48 or 96 kHz, then you can't use DVD-Video.