In strict semantics they are essential because we can't manufacture them, but that's not the same thing as defining an RDA (depleted uranium is also "essential"). I agree that in free-living humans there seems to be no evidence of polyunsaturate deficiency.
Lots of: urban hiking, cycling, sprinting
Lots of: fresh meat, seafood, eggs, organs, tubers, starchy fruits, low-energy plants, meat fat, dairy fat, oily fruits
Some: cured meat, dairy protein, sweet fruits, rice, peas, tree nuts, oily seeds
Minimal: soy, refined proteins, sugar, liquid carbohydrate, grains, beans, refined oils, peanuts