[mactec54]

You can thread with the single index pulse. Linuxcnc supports rigid tapping with a quadrature encoder on the spindle, so many choose to replace the original to take advantage of this.

An Encoder that uses quadrature is an incremental Encoder

It does not matter if it is Incremental or Absolute, the Index Z Pulse, does not change it is 1 Pulse Per Rev on both types of encoders, so this has noting to do with whether the encoder is quadrature ( Incremental ) or Absolute, for a single Index Z pulse stays the same on both types of Encoder