On the Ultimaker Original there aren't many settings stored on the machine itself. You can tune the flowrate on the UltiController.
I don't think there is a specific field in the gcode that tells the flowrate.
The difference I could think of is that printing over SD is safer, because it won't be interfered by a crashing computer or problems connecting through USB.
Could your friend give any examples?
The difference of only 3% may also be to subtle to notice anyways.
Flow increasing by soft and by hardware might be different. You can adjust the flow on the slicer so it extrudes more, or on the machine so it extrudes more. I never do it on the machine. If you do it on the machine it might work different. But there's no gcode to change the flow like on the machine.
Edit: Correction, you can do Gcode to control the flow, like on the machine
M221 S100 ; Set extrude factor override percentageEdited by Guest
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