Failed perisher - can still drive
It is possible, I know this as one of ex-CO's did it (and it was a T23, not a P2000). It's true about the never setting foot in a boat again though.
Both the CO and XO have passed perisher, it allows them to both watchkeep as required.
And for the fact that it's hardest maritime course - it's certainley not by pass rate. The dagger N's have that dubious privilage....