Why do InstantSearch components that use Hooks render twice?

Under the hood, the component calls the setState function (from the useState() Hook) to update the render state of the widget whenever the widget render state parameters changes, so state change triggers a re-render in React.

This allows the first set of results to be artificial (__isArtificial: true), so you can rely on the results without any conditions on the variable being defined or not on first render. The second set of results is populated with the actual results from the API.
 
Here is the implementation in React InstantSearch Hooks.