So those objects are used for references by certain functions in the kit. For example : BP_GenericDoubleJumpWall is an actual object with a wall sprite attached to it and if the player collides with it he can use the wall to jump off it. The spikes one are referenced when the player collides with them to see if he takes damage or not.
The can jump internal function is created by the engine itself and it basically checks if the player is flying or not.
Everything you see in the kit does have a purpose so there shouldn’t be any leftovers in there. Hope this helped!