React-native FlatList not rerendering row when props change

I'm having an issue with the new FlatList component. Specifically, it does not rerender it's rows, even though props that the row is dependent on changes.

The FlatList docs says that:

This is a PureComponent which means that it will not re-render if
props remain shallow- equal. Make sure that everything your renderItem
function depends on is passed as a prop that is not === after updates,
otherwise your UI may not update on changes. This includes the data
prop and parent component state.

THE QUESTION

However, seeing as I change an ID of the selectedCategory item – the prop that should indicate whether the row is 'selected' or not – I believe that the props should rerender. Am I mistaken?

I checked the 'componentWillReceiveProps' methods of both the list and row components, and the list receives the update just fine, but the row's lifecycle method is never called.

If I include a random, useless boolean state value in the list component, and switch it back and forth when the props update, it works – but I don't know why?

state = { updated: false };

componentWillReceiveProps(nextProps) {
  this.setState(oldstate => ({
    updated: !oldstate.updated,
  }));
}

<FlatList
  data={this.props.items.allAnimalCategories.edges}
  renderItem={this._renderRow}
  horizontal={true}
  keyExtractor={(item, index) => item.node.id}
  randomUpdateProp={this.state.updated}
/>

THE CODE

The structure of my code is this: I have a container component with all the logic and state, which contains a FlatList component (presentational, no state), which again contains a custom presentational row.

Container
  Custom list component that includes the FlatList component
  (presentational, stateless) and the renderRow method
    Custom row (presentational, stateless)

The container includes this component:

 <CustomList
   items={this.props.viewer}
   onCategoryChosen={this._onCategoryChosen}
   selectedCategory={this.state.report.selectedCategory}
 />

CustomList:

class CustomList extends Component {
  _renderRow = ({ item }) => {
    return (
      <CustomListRow
        item={item.node}
        selectedCategory={this.props.selectedCategory}
        onPressItem={this.props.onCategoryChosen}
      />
    );
  };

  render() {
    return (
      <View style={_styles.container}>
        <FlatList
          data={this.props.items.categories.edges}
          renderItem={this._renderRow}
          horizontal={true}
          keyExtractor={(item, index) => item.node.id}
          randomUpdateProp={this.state.updated}
        />
      </View>
    );
  }

}

(data comes from Relay)

Finally the row:

render() {
    const idsMatch = this.props.selectedCategory.id == this.props.item.id;
    return (
      <TouchableHighlight onPress={this._onItemPressed}>
        <View style={_styles.root}>
          <View style={[
              _styles.container,
              { backgroundColor: this._getBackgroundColor() },
            ]}>
            {idsMatch &&
              <Image
                style={_styles.icon}
                source={require('./../../res/img/asd.png')}
              />}
            {!idsMatch &&
              <Image
                style={_styles.icon}
                source={require('./../../res/img/dsa.png')}
              />}
            <Text style={_styles.text}>
              {capitalizeFirstLetter(this.props.item.name)}
            </Text>
          </View>
          <View style={_styles.bottomView}>
            <View style={_styles.greyLine} />
          </View>
        </View>
      </TouchableHighlight>
    );
  }

The row is not that interesting, but I included it to show that it is entirely stateless and dependent on it's parents props.

The state is updated like so:

_onCategoryChosen = category => {
    var oldReportCopy = this.state.report;
    oldReportCopy.selectedCategory = category;
    this.setState(Object.assign({}, this.state, { report: oldReportCopy }));
  };

State looks like this:

state = {
    ...
    report: defaultStateReport,
  };

const defaultStateReport = {
  selectedCategory: {
    id: 'some-long-od',
    name: '',
  },
  ...
};