Drum roll...
Not too exciting and no other credits I could see (cool interviews tho).
You could infer none of the people interviewed did the other games since they would have mentioned it I suppose.
Seems like Sakaguchi was supposed to do the music for Final Fight, then called Street Fighter '89 (since he also did the original SF why not that too). But he was super busy and so asked others for help.
I guess they forgot to fix the staff roll?
EDIT:
Setsuo Yamamoto from
this interview:
Mighty Final Fight: main (about half with Yuko Takehara) + SE
Final Fight 2: 1 track only
(also SF2 MegaDrive porting, then Rockman X)