Yes, 6 is the new 4.
The definitions are changing. In a recent issue of ACOG's "revitalize", obstetric data definition issues and rationale for changing the definition of active labor were explored.
The Early or Latent Phase is now recognized by the onset of labor to the onset of the Active Phase. Active Phase is now defined as the accelerated cervical dilation generally beginning at 5 cm for multiparous and at 6 cm for nulliparous.
Below, a CNM discusses the rationale.
To access the ACOG "revitalize" document, click here.