The bitterness that we associate with the flavour of endive, sorrel and chicory is never a bad thing. Certain varieties produce incredibly bitter oils. This bitterness is a marker of the cultivar (olive variety). This characteristic is reduced in a dish.
That feeling of irritation in the mouth guarantees the presence of polyphenols, as does bitterness. Pungency suggests that the oil is of high quality, harvested early and in all the right conditions. It is a flavour enhancer!
It represents all of the aromas that come from the fresh olive the moment it is picked. There is a range of fruity aromas in olives, and olive oil comes from the fruit. They contain a plethora of different aromas.
Observation: all very ripe oils (ripe olives) tend to be similar (limited aromas). All very green oils (bitter and pungent) mask the aromas.
For each terroir and each variety of olive tree there is an ideal time when the aromas are at their most mature.
The oil produced when the phenolic components are highest will have a wide range of aromas, more complexity and a longer aftertaste.