All of those midis come straight from the game's data (I know this 100% because I've worked with some of them recently). The files were originally in .BGM (for sequence data) and .WD (for instruments) formats. The page even blatently says "Instrument and sequence data ripped from the original Kingdom Hearts" in small, grey text. I don't mean to be rude, but I'm a "say it how it is" type of person.
MY FIRST POST ON THE FORUMS. I was discussing this briefly on the Discord server, but on the "MIDI & Instruments" page for Kingdom Hearts 1, https://kh-vids.net/pages/khmidi/, "Dive into the Heart -Destati-" only has parts 2 and 3 (part 3 of which is actually part 4 if all of my playthroughs of KH1 weren't lying to me) when the Kingdom Hearts Ultimania says that there are nine parts total. The point is this; I need your help to find the missing parts (as well as finding the tools to extract them along with the BGM/WD sets for other tracks). Also, I would like to request that whoever was in charge of ripping the MIDI and instrument data to upload the instruments as more compiled soundsets (like .dls and .sf2), if that isn't a problem.