There is nothing in our SOPs either.
There is howver plenty of “wise man’s guidance” from our training dept. My lot have a number of EIS1 old MSNs in the 1xxx range and I was strongly advised not to switch the pumps on until:
(a) refuelling was complete and
(b) the APU was running and the external power had been disconnected.
The reasoning behind the latter was experience showed most “challenging” problems (random ECAMs, CIDS issues requiring resets &c happened when switching power supplies with a high load. Not SOP or in the manuals but wise experience nonetheless!