Also, I think it's important to say that ECS is not the only composition option, you can just use "EC" (or also CES): while on ECS the behavior runs on systems, on "EC"/"CES" the behavior runs on components, which is the case on Unity (by default) and O3DE.
I believe the mentioned Scott Bilas famous talk about composition follows this "EC" model instead of ECS, except that he calls it Game Object instead of Entity.
I believe the mentioned Scott Bilas famous talk about composition follows this "EC" model instead of ECS, except that he calls it Game Object instead of Entity.