Diodes incur a voltage drop which may not be desirable, especially if you already have a 3.3V power source that you can use. I would expect high-end equipment t

Diodes incur a voltage drop which may not be desirable, especially if you already have a 3.3V power source that you can use. I would expect high-end equipment to have a dedicated power supply path for the external connector which would avoid these issues but of course cheaper (or size-constrained) circuits might cut corners and just connect whatever 3.3V power source they have lying around.