Since the DGX-670 doesn't actually have the OrganFlutes processor, these are probably just pre-recorded versions of the voices, without the ability to edit the footage lever configuration.
Thanks for the post!
There isn't an OrganFlutes processor per se. It's a software module that configures the AWM2 tone generator with the selected drawbar registration, etc. However, I think you're right about it being sampled.
Genos (and probably other PSRs) have the same organ style voices. The StyleVoices folder is exposed in Style Creator on Genos. The Yamaha software hides this folder when selecting a voice in Voice mode.
The VCE file adds the "Dual Rotary Speaker Bright" insertion effect. BTW, VCE files are MIDI SMF in disguise. Rename the file extension to "MID", import the MIDI file into a DAW, and look around.
Have fun and thanks -- pj