Did he ever figure it out? All the manufacturers no longer provide this information for new products. My guess is they expect MIDI to finally go away. But, Korg and Dave Smith always kept to the tradition so I was surprised they stopped. Considering Dave Smith invented MIDI.
If only you could read NRPN controller values from the machine, there would be little need for SYSEX anyways.
The change with not listing the SysEx structure started with the Prophet 12 as far as I'm aware, and my bet on why they have started dropping this info is because since the Prophet 12, they began doing "versioning" of the SysEx structure if they wanted to change something... The Prophet 12 is at version 3 of it's SysEx, and when that happened, my own editor stopped working correctly with some mod matrix sources/destination... that was because they put in more, and also sorted them, meaning that a source that had a specific index before, now suddenly had a new index... they did not simply "add to the indexes"...
This means that if the SysEx of a device is getting a new version, any information already out would be wrong... they would have to give out a new document with each new version of the SysEx... even the SysEx length could be changed this way because the synth is internally accepting older versions of the SysEx dump... the dump has a dedicated "version byte" in it, so the OS can always see what version the program was made in, and adapt to it, without the user even noticing it.
This versioning though gives editors a hard time following up if they have to support all the versions...
Rev2 is actually a "version 2" ... the version byte in the SysEx structure says "2"... I suspect that version 1 is in fact simply the old Prophet 8 format because the REV2 can load the older Prophet 08 programs directly...