Actually on the MD80 I think he's refering to the nose strakes. They're there to smooth the airflow across the wing. The spray deflector is mounted on the nose tires.
From the MD80 AMM:
(4) Aerodynamic Strakes - Aerodynamic strakes are installed, one
on each side of the fuselage, just below the flight compartment
clearview windows and compartment floor line. The
strakes are provided to improve vertical and directional
stability during high angle-of-attack aircraft conditions.
On the Beech the fins aid the stability and effectiveness of the empenage controls at lower airspeeds when there's a lack of airflow across the stab because of the T-Tail's characteristics. You don't get the airflow effectiveness generated by the engines that you'd have in a low mounted Horizontal Stabilizer.