I think I have some dates for the Apple games, I'll get back to you on that when I have some more time.
And no problem guys, you're most welcome! I made a mistake though- the Apple IIGS uses channel 1, which obviously the MT-32 doesn't, so the MIDI file needs to be edited or the MT-32 needs to be set to channel 1-8 mode.
"Composed for MT-32" could apply to new themes developed just for the IIgs version, and potentially for games released across multiple platforms including the IIgs simultaneously. "Reorchestrated for MT-32" would be the more technically correct term for anything ported from earlier releases, I think. But also it’s possible as you’ve hypothesizes that everything was intended for the IIgs native sound system (with the Ensoniq chip) which I am led to believe supported an early form of MIDI, and playing on an MT-32, while possible, might not have been intended. Curious: why do you say SysEx wouldn’t have been used on an Apple platform?
Well, the obvious question becomes, "Why would someone compose for the Roland when that isn't what it's going to be performed on?". It'd be like composing the MT-32 era games for some other device. It doesn't make a lot of sense.
The ports are reorchestrated as you say, but they're also often featuring new compositions.
The IIGS absolutely used MIDI, or a close variation of. It was so close to standard MIDI, the resources can simply be extracted from the game as MIDI without any file-altering conversion.
SysEx - the reason Sierra used SysEx was to send patches to the MT-32, and occasionally in GM games to perform a reset. I can't imagine there was any need for it with the Apple games, and also even if the scores were composed on a MT-32, the Apple wasn't using one, so it wouldn't have needed the MT-32 patch bank.
In further news, I got SQ1 extracted, and there's only 4 music tracks. Listening makes me think they are the main theme song (a more primitive version of the SQ2 one) and 3 bar tracks for the Keronian Bar.