Actually, both are involved.
The definition of scissors in air combat does not necessarily have to follow a two-dimensional plane.
In basic concept, it is a maneuver that consecutively changes flight path in order to overshoot the enemy - any ACM concept involved with this type of maneuver will be considered as 'scissors'. Therefore, scissors can be done in all sorts of situations - diving, spiraling, turning, climbing, simply moving up and down, in 2D, in 3D and etc etc.