That's the same conclusion i'm into, but i wasn't sure because i have a rev 0 + unknown os version, so perhaps it could be a bug due to older os version.
But i think it's more a documentation error than broken/vestigial functionality because it's an essential one:
The mt32 patch temporary area reset the timbre temporary area each time you change a parameter.
It's impossible to work like this and the temporary area are worthless. Roland would for sure correct a bug like this.
I've done a trick on cubase to first send the patch paremeters then the partial parameter, that's work on device recall, but without the save functionality is worthless for the unit as you can't save the timbre and patch into memory to make bank.
The last ressort is to use the memory instead of the temporary area, but this limit 1 timbre and patch / part and it's a nightmare to work with specialy on cubase where device making is already a nigthmare... but not on a bcr2000!
Need also to verify that the request mode is good, because the request return something and the documentation request mode is set to send data without handshake (12), perhaps the request should be send in a handshake request mode (40) or (42).
Hope someone managed to work with this request.
Have a good day,