sounds like one operators thoughts based on carryover from previous types or experience or...?
If it was that vital for technical reasons to pause before turning on each electrical hydraulic pump, then Boeing would revise their checklist to warn of the requirement. For example the Boeing 737 Classic QRH on Loss of Both Engine Driven Generators. It states:
Bus Transfer switch....Auto
Elec Hyd Pump switches (both),,,,,,ON, one at a time.
So much personal opinion is taught as a technical fact that you don't know where the bulls#t starts and stops