It's because there wasn't a good way to split them up when I added the rallycross. Although it would be fun, we're not going to allow modding the game for any runs.

I would also like to myself, but as mentioned by FireFox, what is effectively a TT run can just stay on ingame leaderboards. However, here, I would consider adding a full format RX leaderboard, maybe as a separate game to keep things tidy.

Your run must either be a video on Youtube, or something permanent on Twitch. You can then submit by selecting the category in the leaderboards tab, and clicking the 'submit' run button where you can fill out all the relevant information. If unsure about something then leave them blank, and they'll be filled in by one of the mods when reviewing. Hope this helps