I was sort of under the impression that part of the Daytona 3 PC based hardware (a full leak surfaced some time ago) was running HLE emulation, and i wouldn't be surprised if that was done by him as well. The game is just a front end that sits around Daytona emulation, reskinning and interfacing to d3d to show the visuals.
Also wasn't there some other emulation code in there? Bronx or Vipers? I forget easily