I meant not to disable EDID usage, but using custom EDID. Below is some info from NVidia's readme about this option:
Option "CustomEDID" "string"
This option forces the X driver to use the EDID specified in a file rather than the display's EDID. You may specify a semicolon separated list of display names and filename pairs. The display name is any of "CRT-0", "CRT-1", "DFP-0", "DFP-1", "TV-0", "TV-1", or one of the generic names "CRT", "DFP", "TV", which apply the EDID to all devices of the specified type. The file contains a raw EDID (e.g., a file generated by nvidia-settings).
Option "CustomEDID" "CRT-0:/tmp/edid1.bin; DFP-0:/tmp/edid2.bin"
will assign the EDID from the file /tmp/edid1.bin to the display device CRT-0, and the EDID from the file /tmp/edid2.bin to the display device DFP-0. Note that a display device name must always be specified even if only one EDID is specified.
Caution: Specifying an EDID that doesn't exactly match your display may damage your hardware, as it allows the driver to specify timings beyond the capabilities of your display. Use with care.
I'm not exactly sure, but by modifying EDID in some way we can make HDMI audio to work. But I may be wrong.
Anyway, until we know how nvidia driver decides whether to disable HDMI audio, all we can do is guessing.