Problem: M5 will still report a spindle speed about fluidnc HOT 1 OPEN

That might be hard to change because it is handled by logic deep inside the spindle type specific driver code. The name is somewhat misleading. It doesn’t really force the S variable to 0 but rather forces the spindle type specific control signal that the S value orherwise maps to to the same setting that S0 would cause. That control signal could be a voltage or a PWM duty cycle or a vfd command packet or … we used s0 in the name for lack of a better way of saying it in a manageable number of characters.

from fluidnc.