Thanks, mono!
Still, can't get it. We already have running engine generator, which is not weaker than APU generator. APU generator is able to hold all load, but engine generator - not? BTW, it says that any generator is capable to supply all aircraft demand. Why shed? And zero notification (except purser's tirade).
No single remark in the procedure. Is it designed to be this way?
It's not always possible to start both engines at the gate...