With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: In the ATA standard, pin 20 is defined as a mechanical key and is not used. This pin's socket on the female connector is often obstructed, requiring pin 20 to be omitted from the male cable or drive connector; it is thus impossible to plug it in the wrong way round.
text_B: Does it sound like other standards that use this kind of 20-pin connector often necessitate that the plug be inserted one way, but not the other?
YES.