Controller_fan needs a heater?

General Discussion
1

I’m setting up an Adafruit Metro M4 just to run 4 steppers, no heaters.

Based on the CONFIG settings for the controller_fan, one needs to specify a heater, if none, then it is assumed that “extruder” is there?

#heater:
#stepper:
#   Name of the config section defining the heater/stepper that this fan
#   is associated with. If a comma separated list of heater/stepper names
#   is provided here, then the fan will be enabled when any of the given
#   heaters/steppers are enabled. The default heater is "extruder", the
#   default stepper is all of them.

From the looks of how Klipper is responding, the logic requires a heater to be present, not just a stepper.

2

Stepper and Fan config

[manual_stepper z_stepper]
step_pin = PB13
dir_pin = PB12
enable_pin = !PA21
rotation_distance = 2
microsteps = 16
full_steps_per_rotation = 200
endstop_pin = PA19

[controller_fan metro_m4_fan]
pin = PA20
idle_timeout = 60
stepper = manual_stepper z_stepper

Error:

Config error
Traceback (most recent call last):
  File "/home/pi/klipper/klippy/klippy.py", line 162, in _connect
    cb()
  File "/home/pi/klipper/klippy/extras/controller_fan.py", line 32, in handle_connect
    self.heaters = [pheaters.lookup_heater(n) for n in self.heater_names]
  File "/home/pi/klipper/klippy/extras/controller_fan.py", line 32, in <listcomp>
    self.heaters = [pheaters.lookup_heater(n) for n in self.heater_names]
  File "/home/pi/klipper/klippy/extras/heaters.py", line 273, in lookup_heater
    raise self.printer.config_error(
configparser.Error: Unknown heater 'extruder'