You are right, but beware everything you put into the builder function results internally in a setState() call. Just look in Flutter’s source code. AnimatedBuilder uses AnimatedWidget which get the animation controller passed as listenable. Everytime the listenable updates (each animation frame) it calls setState.

The key to performance (of AnimatedBuilder) is the prebuild child that has impact on performance. But only if it’s constant over the complete animation process.