The emu cutoff is because you shouldn't be in a position where you're competing for a top time and still aren't playing on original hardware. The reason dolphin is allowed to begin with is because we as a community decided that the game is more accessible by having an emulator option that cannot be in contention for a top leaderboard time, because more people will be able to use it to get into the game. The leaderboards of some games do not allow emulator at all, and in an ideal world, every serious runner of nearly every game would be playing on original hardware (where it is reasonable to, of course). It should be seen as a privilage that emulator is allowed at lower skill levels at all.

The capture card cutoff, on the other hand, exists because we as a community want to ensure that the runs at the top of our leaderboards are a certain standard of quality (less so to reduce the risk of cheated runs. in fact, cheated runs are harder to do with a potato cam pointed at your tv that would qualify as acceptable video proof for slower times). We as a community generally agree that if you have put enough time into the game to get to the point below what we've set as the capture card cutoff, then you should care about the quality of your runs enough to submit a higher standard of video proof.

This is not to say that you cannot continue to run the game on your own if your way of playing / recording the game doesn't meet these requirements. It just means that your runs won't be accepted to the leaderboards.