That link says O3DE uses EC, not ECS. These are terribly named and often cause confusion, but they are different.

In "Entity Component" systems (think Unity), entities own components that give them data and behavior.

In "Entity Component System" systems (think Unity DOTS), components are just data, and behavior is driven by systems that live outside entities.

They are similar in some aspects and both are radically different than a deep OOP hierarchy, but ECS is quite more hardcore on decoupling. It's been a few years and it's still not unanimous whether adopting Unity DOTS over regular Unity is easy or even worth it, for instance.

Still, Godot isn't very OOP either, working mostly with composition of behaviors.