not really sure about this , but for sure , other documents are recommending not to do it ...
FCOM explicitly allows to start and/or shut down APU
During refuel/defuel procedures, APU starts or shutdown are permitted with the following restrictions:
If the APU failed to start or following an automatic APU shutdown, do not start the APU
If a fuel spill occurs, perform a normal APU shutdown.
you could even have one engine running while refueling if you have no APU/GPU available
where the fuel truck is plugged to the Aircraft ...?
depends on the option your company bought. A320 is available with refuel couplings on either side.
...some other operators simply say ‘ airbus says all white lights out’...
our FCOM has an specific note adressing that
ALL WHITE LIGHTS...................EXTINGUISH
It is a general rule to turn off all the white lights during the scan sequence; therefore, these actions are not listed here.
Fuel pumps shall remain OFF until refueling is completed.
the reason? no word about it