Question du test React (legacy)

Voici un composant censé afficher le nombre de pixels scrollés verticalement.

class Scroller extends React.Component {
  constructor(props) {
    super(props);
    this.state = { distance: window.scrollY };
    this.updateDistance = this.updateDistance.bind(this);
  }
  
  updateDistance() {
    this.setState({ distance: window.scrollY });
  }
  
  componentDidMount() {
    window.addEventListener("scroll", this.updateDistance);
  }

  render() {
    return (
      <div style="height: 5000px"> 
        <p style="position: fixed; top: 5px; left: 5px">
          Scrolled {this.state.distance} pixels.
        </p>
      </div>
    );
  }
}

Quel(s) est(sont) le(s) problème(s) ?