The extruder switch is handled by the M2000 gcode in the tool change gcode that Snapmaker coded into the marlin firmware and that @macdylan explained here. That one looks quite fine to me.
Why G4 S0* commands are being commented out is unsure - the comment suggests that a dwell command of less than 1s causes problems with the Snapmaker M2000 command. @ne0xys is my assumption right about that?