I agree it'd be cool to get some competition going here, but I can't imagine that further fragmenting the leaderboard would solve that.

Right now, if a person wanted to be the overall best at, say, Normal Long, they'd need to hold 1st on definitively above 50% of the maps just for Normal Long. But each map can take some practice and optimization to find a serious PB on. So, with the time investment if a real competition did kick off, it would take probably 3-4 players per difficulty/duration pairing to really be a visible competition to bring down times.

You might be able to see overlap in up to 3 categories from casual runners at a time, but that still means 12-15 people competing on times to have competition across existing solo categories. Adding a category for every single perk on top of that means 10+ the number of people to really push times.

Any less and people are really just throwing times at the wall to see what sticks.