but then, they're the type that expect an sop with exact measurements on how to wear a hat.
Would love a copy of that SOP, would not be surprised if it actually exists.
Long time ago I saw an ATT&T, aka 'the (American) phone company' manual that had over 10 pages on how to use a screwdriver. Wish I had kept a copy.
As to chargers, as many have stated almost all are now switch mode that have a very wide input range and frequency tolerance.
Suggestions that input power quality would affect the (typically) 5V output which in turn would affect the devices internal battery controller are false and possibly marketing driven. (Resist temptation to start a 'golden ears' flame war on gold plated welding cable for speaker wire
Grounding difference are possible but doubtful they would be a safety issue since any 2 prong device has to be double insulated to be safe in normal use.
Grounding could affect EMI but even that is likely more sensitive to cable placement than anything else.
All that said when it comes to cockpit use it is either SOP/approved or not and anyone deciding that it is not relevant is on their own.