Having written Unity, Godot, Unity DOTs, Bevy, an obscure ECS engine called kivent, and even rolled a java engine from scratch at one point I somewhat disagree with this statement.

When people think of overhead, they might be thinking of the jankiness of Unity DOTs and it's lacklustre ECS integration with a preexisting editor designed for Unity's Gameobjects world.

The truth is, an engine built with ECS from the outset has ergonomics that go beyond merely writing better multithreaded code. It truly enforces composition over inheritance when done right. Overwatch is an example of a game written using ECS that generally doesn't have hundreds of thousands of entities bouncing around