The IGT and RTA categories are definitely needed. Lots of people won't understand why this is important and a good idea intuitively because they don't know how the IGT works in this game.

How IGT works in this game: -goes up by one second every n frames (I'm not sure the exact amount) -goes down by one second every time you kill an enemy -goes up by 20 (twenty!) seconds every time you die

Because of these peculiarities the strategies for RTA and IGT are very fundamentally different. A deathwarp that saves ten RTA seconds can cost lots of IGT seconds because you could have potentially killed enemies along the way instead of paying 20 seconds to skip back to your most recent save point.