Are the IL categories only in the Level section due to their difficulty?

Also slightly related, but is the lack of any other challenge categories (like Katana on the main boards) being on here because either nobody's done runs, they're not viable, or they're too similar?

The level ones are just there because it's what we thought of when designing this page with the SH discord back in the day. I'm no longer in that Discord, but generally these boards haven't changed in a long time. Katana being on the normal boards is because it's a challenge built into the game, not an arbitrary one made by the community.

Right. I mentioned Katana as an example, I get why it's on the main board. Would it be better to just ask in the Discord about this kind of stuff?