The M628 S0 code (marked as TODO) almost certainly does a nozzle purge.
Check also this link where they actually describe how to remove this command to avoid needlessly purging filament:
https://wiki.bambulab.com/en/ams/manual/ams-not-unloading-to-save-filament
The
M628 S0code (marked as TODO) almost certainly does a nozzle purge.bambu-p2s-gcode-annotated/machine_start_annotated.gcode
Line 259 in 990d253
Check also this link where they actually describe how to remove this command to avoid needlessly purging filament:
https://wiki.bambulab.com/en/ams/manual/ams-not-unloading-to-save-filament