A spoiler is an airfoil with both surfaces exposed to laminar flow of the same initial and final velocity designed to generate lift in a particular direction.
A vehicle hood is clearly not comparable, except to someone trying too hard to out-smart the internet. A hood is more like the roof of a house: static atmospheric pressure on the closed side, dynamic flow / pressure on the exposed side, causing uplift and load reversals in a direction that is not desired.
Most people assume it's air ramming through the grill or engine compartment pushing the hood open from below, but it's the air flowing over the top that is causing the pressure differential. The hood would want to fly open even with a fully blocked off nose and under paneling. 14.7 psi static atmosphere on the under side + moving fast enough to reduce the top side to half of that = 17,000 lbs of uplift on a 4 foot square hood. A mere difference of .2 psi would cause 500 lbs of uplift, more than enough to lift a 50 lb piece of plastic/sheet metal.