I think you misunderstood my bad attempt at humor.

If the PIC of a Part 135 flight illegally handed the controls over to a non-qualified pilot, the non qualified pilot could log the time as PIC under 61.51, since 61.51 doesn't care whether the activity is legal or not.

Just an extreme example of the difference between the logging rules of 61.51 and the operational rules in other parts of the FAR.