Depending on the motor, the audible warning indicates 'something is wrong',
which can include low oil pressure, low outdrive fluid in the reservoir (I
had that happen at about 10 hours and took forever to figure that out),
engine overheating and other things that the motor mfr decides are important
enough to warn you to shut down and figure out what is wrong.

I'd say that the audible warning for anyone in the water is a 'bonus' of the
system, I doubt it was thought of at first as the primary use.

The oil pressure you reference is pretty normal...I get that running
Valvoline Racing straight 40.

SL