Just tested on my Dreamcast and the issue is there, finished the race with player 2 and nothing and then finished it with player 1 and player 1 won. No sound effects for player 2.
In the options menu there is a vibration effect control, vibration doesn't work but isn't listed on the back of the case. Tested Roadsters which is like a poor N64 game now to test my rumble packs and they work.
The steering wheel also works but don't play with it on your lap lol
I've reported the issue via the kickstarter page as I was a backer.