I wondered the same thing and I found this YouTube on how it applies to diodes…Alex is free to answer and remove my link. I just thought I would try to help..
Voltage drop the way Alex is showing it is the measurement across a FET’s terminals in diode mode, with him showing you the correct readings and incorrect (shorted).
If you use a voltmeter to check voltage across a resistor that has current passing through it, that is another thing altogether.