One diagram understands all of the following terms.

Bio-based vs Fossil-Based Plastic
Oxo degradable vs Bio degradable vs Compostable

For example, Eco PE?

The ECO PE is either oxo-degradable or not degradable at all, please see the diagram in the spec sheet. if oxo-degradable, it is only degraded to be some plastic powder which is harmful to the environment and humans, such as going to the waterway. Or, it is bio-based PE but not degradable because the molecular structure of PE is fixed, it cannot be biodegraded.

Therefore, which plastic is truly eco-friendly?

Bio-degradable and Bio-based Plastic such as PLA, PBAT, and PBS are truly eco-friendly plastic type.