All the cool kids are doing it.
SRAM's excellent new Guide brakes ushered in an all-new rotor design as they stepped onto the scene, and it's not just a new machining pattern. It's called the SRAM Centerline Rotor, and it relies on a new profile to keep the braking track straight and to better control cooling.
The name "Centerline" is derived from a series of elongated vents positioned directly in the braking track. The new design also incorporates a 12-spoke design, which is bumped up from the six-spokes of SRAM's existing models. This new profile was designed to control the rotor's warping and other lateral distortion that can occur when heated, in addition to aiding in overall cooling. The result is minimal vibration through a consistent center of friction, thus ensuring braking is predictable, quiet, and smooth.