Yeah, the Dark Race is really annoying. I saw that some emblems were missing
(which were, of course, Hero and Dark), and I eventually found out that both
gardens have to be opened before both races can be entered.
(I had a Hero Chao and Hero Garden, but I couldn't enter the Hero Race. That's pretty weird.)
It was also frustrating to win. I used the glitch for a while, but I was impatient,
so I got my Chao just almost good enough, and then I tried the races until I got lucky.
Oh, and that Green Hill stage shows why an old StH-style side view and a 3-D
stage with a character that moves in all directions don't mix.
(just like Wario World's annoying outdoor Glue Globe areas, or the end of Sky Deck)